First of all yeah, you do get buildings from the same place, just keep buying till they end more or less. H-scenes kind of open up when the girl starts getting more and more corrupted so the rich guy is kind of a good place to begin, just beware his wife, in more way than one. She will give you eventually a job as maid, which will make you unable to whore yourself to the guy, making the prices for upgrades and buildings steep. (They come down from having fun with him) And doing the maid job enough will lead into a dead end eventually.
Requests are done in the bar, the bartenders first 2 options are accept requests and complete requests, they vary between just complete thing by wasting some time on it and complete by collecting the items he asks. Pretty simple tasks more or less.
And the guys you hired were mercenaries, if you want them to be loyal, you need to pay the price they ask and not go for the cheaper option, that's when they betray you.
Dungeon itself seems to be randomly generated and brutal so getting help there really makes it less of a pain, just either make sure you can pay the mercs or trust on the "player" marked characters. I myself didn't do much of dungeon so I can't help on that regard. Though I can recommend equipping combat skills as, magic seems way underpowered for the automatic combat enemies...
