Does the owner of a foreign company need to pay taxes in the country of residence, if he does not receive any money from the company? Imagine someone in Austria, let's call him Franz, registers a company in another, non-EU country. He sells some services in the name of the company. The company gets paid by its customers (the money goes to the bank account of that company). Franz does not pay himself a salary, nor does he take money out of the company in any other way. The company pays all required taxes in the country it is registered it. Also, Franz puts money into the company. Franz has a job in Austria and his employer deducts all required taxes and fees from his salary. Whatever money Franz receives from his employer is already after-tax. Does Franz need to pay taxes/fees in Austria for the earnings of his company, if he does not get any revenue from it (neither salary, nor dividends, nor other money flows from the company to him)? If yes, what taxes or fees does he need to pay? Note: If you don't know the Austrian regulations, but know German ones, please provide the answer for Germany (as the laws are similar in both countries).
what taxes or fees does he need to pay? According to this glimpse of Austrian tax law, Franz would still have to pay income tax on any non-monetary compensation he gets from the company. See section of "Vermietung und Verpachtung [...]". Non-monetary compensation is typically known as benefits. The term serves to distinguish that compensation from (1) any cash flows from the company to Franz, which you ruled out in your description, and (2) any expenses the company incurs for business purposes involving Franz. Your mention that "nor does he take money out of the company in any other way" might mean that you ruled out benefits as well. I just wanted to be safe and preclude any misunderstanding in case you had in mind only cash flows from the company to Franz.
In business dealings, you would have a contract with a company, not with its owner. The new owner inherits both the assets and liabilities of the company. It's up to the buyer of the business to do due diligence before buying the company. The old owner may escape obligations to clients and suppliers once the sale of the business is complete, but the new owner could sue the old owner for fraud. (It may be possible to escape some liabilities by declaring bankruptcy, but that's not the situation you described. One unethical accounting trick that a company can use is to split the company into two corporations such that one branch inherits the liabilities, and it go defunct.)
You are a resident of one state, and a non-resident of the other. Or you could be a "part-year resident" of both. Read the applicable personal tax rules for each state, or hire an accountant to do it for you. Note that, in the end, each dollar of income is only taxed by one state. It's figuring out which state that gets tedious.
The criteria used by the IRS suggest that for federal tax purposes, the cashier would be properly classified as a contractor. Behavioral Control: A worker is an employee when the business has the right to direct and control the work performed by the worker, even if that right is not exercised. There is probably some training involved here, but it seems negligible. Has the company actually retained the right to direct and control the cashier? Is he obligated to use their register, as they tell him to use it? Is his work evaluated for compliance with those instructions? I'd guess that in most cases, the company doesn't actually care about any of this. As long as the company got all the money it was owed, would it really care if the cashier just stuck the money in his pockets until the end of the day? I'd also argue that it isn't really the employer controlling the when and where of the contractor's work, but rather the circumstances. Classifying him as an employee because he has to be at the event doesn't really make any more sense than saying your plumber is an employee because he has to come to your house to do the job. Financial Control: Does the business have a right to direct or control the financial and business aspects of the worker's job? The investment in the cash register seems relatively nominal. The company probably does not reimburse the cashier for expenses incurred in getting the job done. The cashier is presumably free to offer his services to others. The cashier is presumably being paid a one-time, flat fee. As you noted, though, the fact that there isn't much profit-loss opportunity is one factor pointing in the other direction. Relationship: The type of relationship depends upon how the worker and business perceive their interaction with one another. The fact that this is a single, hours-long job is probably the strongest evidence that the cashier is a contractor. Further, the cashier's job is not a key part of the business, as it is only a minor portion of an event that the company has never performed before and has no apparent intention of repeating. I assume that the company is not providing health benefits, sick time, etc., and that any contract with the cashier includes no language suggestive of an employer-employee relationship. Conclusion: The employee-contractor distinction is pretty fact-intensive, but based on what you've provided, there seems to be a much stronger argument that the cashier would be a contractor.
Since Germany and Spain are both in the EU, there is really nothing special you have to do that would be any different from moving money from one account in Germany to another. Indeed, if you deposit money into a bank in Germany that has branches in Spain, you ought to be able to deposit it in Germany and withdraw it in Spain. You could also wire the funds from one bank account to another. Or, for that matter, you could withdraw all the funds in currency form and travel from Germany to Spain and put it under your mattress in Spain. You owe taxes without regard to what you do with the money that you are paid.
The only reason you couldn't take all the profits is if your business were a C-Corp. I don't know of any reason a single-owner LLC would elect to be taxed as a C-Corp. Multi-owner LLCs and LLPs are, for federal tax purposes, either an S-Corp or a C-Corp. When possible they can and should generally elect to be taxed as an S-Corp. IRS Pub 2553 lists the criteria for S-Corp election. (Employees have nothing to do with the question.) For tax purposes partnerships, sole proprietorships, and S-Corps are "pass-through" entities that are not expected to pay a corporate tax. In effect, whether you like it or not, you do pay yourself all of the profits each fiscal year, and they are taxed accordingly.
As written, your question seems to ask for legal advice in a specific case. That would be off-topic. If you are asking strictly as a hypothetical: In germany, there is supposed to be the Bestellerprinzip for services of a real state agent (whoever retains the agent pays the fees). This was clarified in the Gesetz zur Regelung der Wohnungsvermittlung as changed in 2015. Landlords and real estate agents are frequently trying to get around it, but getting the legal construction of the contracts wrong would mean a substantial fine.
If you are the CEO of a public company, this might be a problem if it causes less profits for the shareholders. They could fire you if your actions cost them money. If you are the owner of a business, then the CEO of your company (you) can do anything legal that all your shareholders (you) agree with. Nobody can force your company to deal with anyone, especially with no business, except for existing contracts or if there is illegal discrimination. Now all this is not “your personal opinion” but “the ceo running the company according to the wishes of the shareholders”. You are allowed legally to discriminate against a company whose business practices you don’t like. You have to do nothing, just don’t deal with them. If Facebook sends you a million dollar order, just don’t accept it. Make sure that no sales contract is created. It is remotely possible that you have problems if such a decision causes you to go bankrupt and you can’t pay your taxes or debt, like a debtor could claim you could have paid your debt and want your personal money instead of your broke company’s money.