Houses and appartement

Hello, on my server i would like allow clients to buy houses or appartements and garages.
I saw on a few servers that they had the blue circle (for houses) like in GTA Online. Does this mean that we can do that? (and how?)

Other question: is there a way to use GTA Single Player Mods on a FiveM server?
(lua mods? dll mods?)

Thanks

@Piit3r it can be done, obviously others already have done it. It would require an extensive amount of knowledge on Lua and database connections. The amount of code to accomplish that would be staggering. It’s definitely not something that is going to be made a public release.