Some of the financials are in the replies. He'll get $50k ish for taking part in the IPP, and if he makes a full practice squad he can pick up around $220k for the regular season. If he somehow makes it on to a roster and earns a full time contract then that would jump way up, $3m per year is about the current average although that is boosted by guys like Tyreek Hill earning $30 million a year.
If it doesn't work out he'll still be able to fall back on likely offers from France and Japan.