The V10s are great engines. If its been well maintained it should be good to go. If its been abused I would steer clear. Sometimes it's hard to tell how a vehicle has been treated. I have been burned by buying a previously abused vehicle and it was not fun. You may want to have a trusted mechanic look it over before you commit. Good luck.
2015 F150 Lariat FX4 3.5 EcoBoost SuperCrew
2007 F150 Lariat 4x4 5.4 SuperCrew