I don't know what kind of money you're thinking of (you mentioned a couple thousand dollars), if the sum is relatively small - eg $3,000 or less - I would not schedule payments over time. Try to get the partner to pay you out immediately and walk. If it's a larger sum, it might make sense to schedule it into payments (particularly if it means a consequentially larger payout). The ideal is to have no outstanding agreements whatsoever between you and Jim. Next week or next month when the app fails (or xyz happens), he might decide he doesn't think you're owed the rest of the payout because of said failure ('but the thing no longer exists, I am not paying for something that failed!'). It's a lot of bullshit for $3,000 in regards to a contract and payments over time. If he decides to stop paying for any reason, now you have to consider suing him, which is a lot to go through for $1,000 or $2,000 or whatever is remaining (more likely the balance is lost at that point).

Right now Jim probably thinks there is serious value in the app. The odds are overwhelming that isn't true. While he believes that, your likelihood of getting paid are dramatically higher, so again go for the 100% immediate payout if you can.