system
Given the following post, respond as if you're commenting on Reddit:
human
[General SF] I am in the Market for a Secret Lair. What Should I be Looking For? Any Suggestions on Resale Properties?
gpt
A lot of rookies make the mistake of getting a lair that's "secret" like in a cave or something.  What they fail to realize is that "secret" just means annoying adventurers and heroes will come sneaking in all the time and start causing trouble within anyway (not to mention random people will stumble in from time to time and just be annoying.)  And to make it worse, caves are usually cold dark and wet so you're stuck being miserable in a cave and they'll still find you anyway.  

best option is to go for a big fortress or tower, something that just proclaims your power so that everyone in the surrounding area knows you are there and to be feared.  

Ancient fortresses are good ideas if you don't want to build your own, also ancient tombs can have good aesthetics but just make sure that you do some good remodeling to make it more pleasant to live in.  

Make sure you have a throne room or inner sanctum of some sort, preferably with a throne to sit in and look menacing in.  You want to make sure the light is just right so that you get the properly menacing feel to the place.  You should also make sure the room is big enough for a fight with your enemies and, very importantly, don't store anything that can blow up or otherwise cause you an ironic death, in the room with you. 

as for interior decorating, you want to make sure you focus on buying: Good Prison Doors, locks that actually work, a secret escape route of some sort, and plugging any holes in the wall people might use to sneak in through or listen to your evil plots through.  

How do you afford all that?  Well first off aside from your throne room or inner sanctum don't bother decorating the rest of the place, it will just get trashed when adventurers come through and steal your stuff anyway so don't bother leaving anything valuable lying around.  

You can also save a lot of money by...scaling back on safety regulations.  Yeah the unions and safety regulations call for hand rails and safety measures along the edge of bottomless holes and at the top of towers but really, when are you ever going to need them?