Show me the money!
[tl;dr: old perv wants to pay for her education]
I am in a loving and faithful relationship that is genuine, and I am completely happy. Recently, I've had to make some serious career decisions like to go back to school with the goal of eventually leading a comfortable life and not have to struggle for money.
The man I'm dating is struggling financially as well. While he is loving and giving, if I want to live the lifestyle I do, I will have to be the primary bread winner. I'm fine with that and so is he.
Here is where the predicament comes in. Going back to school is a huge undertaking. I have no support from family and his income is unreliable. However, there is an old man I know who is extremely wealthy and wants to finance my education, give me a place to live and pay for all my expenses in school. He claims it's because he is my friend, he wants to help me and there are no strings attached. He also wants to "get together" with me a couple of times a month. He has an open marriage such that he and his wife are leading completely separate lives. He claims he would help me even if we didn't fool around, and insists that if we were, it's not cheating because of the agreement he has with his wife and the fact that I'm not married. He tells me it's also not cheating because he can't get an erection. Still, the fact is he wants a sexual relationship. I've told him I don't want to cheat on my boyfriend, but I that I really need the financial help. He's already bought me a car.
Even though he claims that there are no strings attached and he wants to help me out of the goodness of his heart, my better sense tells me that nobody does anything for free and my unwillingness to cheat will severely impact the help I receive.
I just have a sinking feeling in my stomach lately because the impoverished girl in me is saying "do it!" but I would be devastated if I hurt my boyfriend or lost him. He would never go for it if he knew. Old man and I get together for dinner once and a while (my boyfriend knows but sees the relationship as father and daughter than old horny man and hot young chick). What he doesn't know is that he keeps putting my hand on his crotch and initiating a hookup. I resist, but he keeps trying.
I don't know what to do at this point. I want a secure future, but scared that it will come with a devastating price if I continue being friends with Old man. Any suggestions?
This is simpler than you think. Even if you didn't have a boyfriend, this is a very bad idea. Your funding, and by extension, your peace of mind, is going to be subject to this old perv's whims. There are lots of ways he can continue to manipulate you even after he promises to cover the costs: stop payments, asking for money back, making you feel guilty, etc. I have seen very similar things happen.
On top of that, you're putting yourself in a very uncomfortable position, subjecting yourself to a glorified version of prostitution. Your integrity is more important than any amount of money and will take you further.
Tell the old guy you're not interested in any kind of romantic relationship and do what everyone else has to do: look into scholarships and loans or find a state school to go to. The tuition is much cheaper. Stop entertaining this possibility, it's bad, bad news.