Cam and dating is the way to go (after of course using MILF programs, as this is your niche).
Ashley Madison pays up to $200 per membership, and they support PayPal. No specific MILF niche, though, but the regular Adult one is working pretty well.
Fling and MeetLocals, which are two sites run by Huge Traffic, pay a flat $35 per sign-up, and they offer MILF banners (among many others).