I think he will be a "bad guy". I mean, he explicitly says he's not looking for profit investing in his agency. So if you set up a business with hot girls involved and you don't care for profit, there's only one possibility, his objective is fucking hot wannabe models. And both times Billy and Lena talk she might be drugged, that makes me feel drugs will be involved in his path.
As I mentioned, I can see it going either way, and much of that is tied to my feeling that this game could end soon or go on for a while. If EK completes the story by chapter 16, I think the chances that Billy's agency is legitimate are higher since it would quickly tie up lose threads. If the story goes to chapter 20, the likelihood of it being a scam are higher. At this point, it's Schrödinger's agency. It is both good and bad until we find out how much story is left.
After the Never have I ever game and the incest question, I don't think Lena's step dad will be her "real" dad. That would make the possible incest real and I think Patreon and Steam don't like that very much.
As long as Lena never actually sleeps with him, I don't think it would be a problem. I doubt a bit of flavor text would really have an impact. Then again, I don't work for Patreon or Valve, so what do I know?
That does remind me of some inconsistencies in the Never Have I Ever game. Sometimes if Ian does something in the game, such as record himself having sex with Lena, it will force him to answer correctly, but others, such as the blowjob in the bathroom or a threesome, it doesn't. Ian doesn't even really acknowledge the threesome with Jeremy and Alison in the game. Also, the game doesn't seem to consider having sex in the ocean as public sex. If Ian tells Lena he had done it in the past, it doesn't impact the game. Similarly, if Ian and Holly have sex in the ocean, Holly will say she never had public sex but will admit to having sex in the sea. Probably more work than necessary for EK, but it is something I noticed.