Constant way to make money is work with Alex in cafe. One-time money getting can be done with first come to Hotel (you will receive free money to test boys/girls here but you can just go home) and first testing bet in Fighting Club if you follow Jay route. New ways to make money will be added in next updates (like repeating bets in Fighting Club and weekly money from mother for first month of game).
About characters. You can just look at main menu. If we count relationship goals right now there is 7 (Alex, Jay, Uma, Ichiro, Steven, Evelyn, Elizabeth). If we count overall characters which will have their routes in future - Samael and Belfagor. Also plot char King (guy with half face covered). Near time will be added Gluttony. Also bunch of random chars which used in some activities like Fighting Club, gym coach, Hotel staff, slime char in events etc.