I would take up your friend's offer and let him do the food plots for now. In the future when you are more comfortable with tractor operation etc you could take over if you so desire.
Regarding what models to look at, new and used, I would make a few points from my personal experience and other points on general principles.
First, I can highly recommend any of the Kioti DKse tractors from 35hp to 50hp. I own a DK40se and it is IMO still the best bang for the buck in the 40ish HP tractor world. Solid, reliable, strongest loader on any 40ish hp tractor and a pleasure to operate. The DK35se is a bit smaller than the 40, 45 and 50 but excellent. The 40, 45 and 50 are identical except for engine bore and stroke. These DKse series Kiotis were supplanted a couple of years ago by the Kioti NX series. Only major difference is the engine which is Tier III on the DK and Tier IV on the NX. If it were me today I would probably first look to see if there were any old stock new DK's around but wouldn't hesitate to get either a used DK or a new NX.
On general principles I would next look at Mahindra and LS as two other "bang for the buck" brands that are well respected and every bit as good as the Kioti. Compare functional properties like loader capacity, 3PT capacity, tractor weight, ergonomics of operator station etc rather than just selecting on the basis of horsepower.
If I were looking for used then Kubota and JD will be more readily available simply because more of those are sold overall and more therefore show up on the used market. A previous generation Kubota is an excellent excellent tractor. The only real difference between previous gen and current gen Kubotas is the new fangled HST transmission and tier IV engine on the current model. The new electronic transmission is nice but hardly necessary. The older Kubotas have essentially the same generation HST transmissions as the current Kioti, Mahindra, LS etc. My point is not to knock the new Kubota HST but rather to point out that Kubota (and others) made their name with the older generation bullet proof HST and those older models still do the work just fine. Regarding Kubota models in the 40hp range, you will be looking for L or Grand L or MX. I'd personally choose the MX over the Grand L but would be happy with either. The L is a basic no frills tractor but still excellent. Kubotas (and JD) are generally lighter and have lower capacity loaders at a given HP size (exceptions exist) so do compare multiple specs not just HP.
I don't know the JD models and my personal bias is that green paint costs too much but there is no knocking the quality or convenience of having a JD either.