As far as his contract is concerned, per the CBA, he's locked into what he would be getting as an UDFA. So $435,000 his first year that than increases his 2nd and 3rd year.
Now if El Pegual says "Hey if you cut my grass on the weekends, I'll pay you $20,000/hr" I'm not sure what the NFL can do.
EDIT: I'm wondering if the Bills and/or other teams offer Collins a nice sponsorship deal that'll put a little extra money in his pocket