The pull-type combine you want is the Case 66 or 72. It is the best supported these days. Some of the old JD units (models 30 - 40?) are too, but the Case allowed a corn head - at least some.
Problems:
Finding one. In good shape.
Maintaining one. You will be doing your own work, and a combine is _the_ biggest thing to maintain - by far.
Keeping it covered. They need to be in a shed, or they rust through in a year or 2.
A tractor to pull it. They are very big & very heavy & like to sink into the ground very much and they pull to one side. You need a good 30 or so hp _utility_ tractor to manage it. A CUT is too light, you will bog down & have the tail wagging the dog.
For small grains, you probably need to swath it. Weeds are the problem, an old combine can't handle green stuff, so you need to cut it, wait 3-5 days, then combine it.
For corn, _storage_ will be the issue. You need the corn under 15% moisture to store as kernals, under 30% (under 24% is recommended) to store it on the ear in a crib. It is _real_ uncommon to get corn under 20% in the field. And old combines have a hard time handling corn anyhow.
You are in an area where this small equipment brings premium prices. Here in MN that stuff sells for scrap iron. $50 will get you a parts machine, $100 will get you a working one - if you can get there before the iron man...
A Gleaner K combine (or newer K2) is a great self-propelled machine - 2 row corn, 10-13' bean header, can still get parts from Agco. They sell for $500 or less with at least 1 head, if not both heads 'here'. Again, you are in an area of demand, whole different thing. An equivelent JD is the 45, but JD doesn't support them as well any more.
--->Paul