Long ago I Used to take on my neighbors places on 50/50 basis.... I provided equip and labor, took my share and left theirs lay.
Learned a lot as I went along..for example: the customer is not equipped or able to move their own hay. Now the same places are 75/25, I take mine and stack theirs. Usually, I end up selling the customers hay (or buying it for resale) for them and collect a fee for that too.
Consider your investment in machines, your maintenance and depreciation, your fuel, labor, and missed family time. You're better off leaving your equipment parked and making your payments than wearing stuff out on somebody elses place just to have some guy fun.
One rule: if it wasn't harvested last season by somebody then I usually won't even look at the job. If I think it might be attractive and convenient location I don't take the job without a thorough walk thru to identify hazards: wire, car parts, re-bar, t-posts, tires, bathtubs and sinks, holes, rocks, ...
Nobody around here irrigates or fertilizes except me on my place. So any custom work results in an inferior product. Generally I don't even want a share anymore. Minimum fee set at $1500 and up from there...weeds out most of the small acre folks.