Fundraising site

Hi, I am a new user here and I hope I am posting in the right place and using the right tool. I thought I needed something not so difficult, but I 've not been able to set it yet.
I would like a site with two kind of users: 1) company - insert its own fundraise ad 2) private user can give money to support a project. I did so many tests that i am reinstalling WP at the moment. So my first question is? Do I need to install WP Multisite or a user can manage his own PP account (to be paied) inside a normal WP site?
Thank you