Like was mentioned.
1. Find an FFL to do the transfer and his cost
2. Find a buyer and decide who pays what for the service.
3. Meet the buyer at your FFL to complete the sale.
It's simple and straight forward. Since using an FFL is not mandatory, expect the buyer to refuse to pay for the cost of the service. You may also lose a sale if the buyer does not wish to go thru an FFL for whatever reason. If it's a rifle in demand and is priced fairly you should have no problem finding a buyer who has no issues with using an FFL.
Fool me once, shame on you. Fool me twice, shame on me.