It depends on the company. Some I wouldn’t touch with a ten foot pole, some are welcome.
Getting you to replace all your links with theirs for rev share or CPA is not a good thing.
This needs to be a flat rate deal. Always ask for the money up front when dealing with someone you don’t have a relationship with.
Make the deal for a trial period, one or two months.
This sort of deal can be sweet if both parties get what they want. During the trial period, you want to see stats in their aff department (if they have one). At the end of the trial period you can renegotiate and adjust the fee.
And again, I have no idea what to tell you without knowing who made the offer.