How do I build upgrades for the mansion? Like the beauty salon, etc?
You have to recruit new models, 1st clean any extra rooms then redecorate them (they all cost 500). After the 1st one is ready you just go the the laptop to put out an ad for the room(s) (you fortunately only have to do this once). After a few days, you'll get a whole bunch of new emails that are all applications to the mansion. The beauty salon isn't specific to any one girl, pretty sure the only one is the BDSM dungeon. All the upgrades are as follows (I may get some of the costs wrong):
Beauty Salon - cost $1000 and lets you begin the MC's transformation (your choice)
Pool - $1500 Gives extra energy to you and can randomly give it to the girls and lets you host a pool party (1 time scene)
BDSM Dungeon - $2000, used exclusively by one of the girls and mostly just serves to unlock scenes
Milking Station - $1000, lets you drink & milk "protein" to gain another energy (does stack w/ pool). This can be sold at the gym & you can be milked if you completely transform
Freelance Floor - $1500, mostly just contains a couple random scenes that you can see at your leisure, it also earns you a small amount of money every day