I agree with starting small and I'd fence off an area of maybe half an acre and let the rest for sheep who will tidy up the grass/weeds left by horses and leave you a nice lawn aswell as bringing in a few pennies. Hay would then be a possibility and make more money if you can get it well made, the price of hay now is ridiculous
I had various experimental crops to see what I could grow but discovered that I don't actually like broad beans which grew well, and I get heartily sick of green beans after a while but tolerate them well enough in other things once they're frozen so they stayed for the space they need (a single tripod is enough
). I grow things I want to eat but which cost more, rather than things I eat a lot of but are dirt cheap by the sack such as potatoes and carrots both of which I can get from local farms for a couple of quid.. I grow beetroots, spinach, all kinds of salad leaves, rocket etc as the price of bagged salads is ridiculous and I eat a lot of leaves
, onions (red and white), leeks, PSB, peas, shallots, and I try a few new things each year eg sweetcorn, sunflowers (seed variety), chard, turnips, cabbages etc. I am pretty poor on brassicas generally other than PSB but always try something, kale, savoy, red cabs, calabrese.. usually end up with just PSB but this year have tried sprouts tho I don't think I like them I am willing to have a go at "real ones" to check and they seem to be growing quite well - sods law maybe cos I could eat calabrese every day and can't get it at all
Whatever you try, make sure you'll want to eat the results or there's little point, you'd get more money renting to horses than anything else so it has to be about the enjoyment