There are a number of provisions in the code that contain relatively clear rules. Most of them revolve around the concept of conflict of interest and then private interest. Generally, writ large, the rule is you don't take advantage of your office for your own private gain. Your public duty and your private interests have to be kept separate. That's a kind of broad-brush commentary.
There are a number of specific rules that apply to that. I could go through all the rules. The gift provisions are quite direct. You can't use insider information. You can't use your influence as a member to influence somebody else to further their private interest, and that sort of thing. None of those relate to the fundraising issue, but they're all different rules.