40 acres is a sizable operation for hay.
Actually, it a little bit big for Ďcheap worn out oldí equipment and itís kinda small for Ďreel newí equipment.
You will have to be careful to be frugal but have reliable equipment, and the time to make the hay when it is ready, not when it fits into your schedule......
Those 850 balers are pretty old. They do a good job feeding, but those chain and bar balers do not make a very tight bale. They do well in grass, but they do knock a lot of leaves off in alfalfa. There is a reason no one makes that style baler any more.....
If you are a handy mechanic you can probably keep them running forever, but if you are new to machinery you are taking on a big learning curve.
If I were looking at 40 acres and wanting to sell top quality hay, I would look for a newer baler that names a better bale. I think you might be in a $5000 budget area for a good baler.
Now, I farm with an old Vermeer 605F baler, it is a belt baler but not much better than you are looking at. I bale about 25 acres of mostly grass hay and 5-10 acres of straw. I also have a small square baler, do about half round and half square. My round baler cost $1600 quite a few years ago.
Iím looking for a better round baler, what I have is getting hard to maintain for the few acres I cover.
Good hat is about being right on time. A couple hours too soon or too late baling can really make poor hay out of good hay. Many the time in lucky to have both balers, can pull out the other one if one breaks down, get the hay made. Iím in the humid north of minnesota, rain is always just around the corner you canít wait to make hay here and you canít get the hay dry.
So, you need to look at your business model. Also what kind of hay, and your location - the more humid East, or the bone dry west. Do you get one, two, 4 cuttings of hay a year. And so forth. These answers might change my opinion on what you need, so take what I say with a grain of salt.
Scrimping on a very well worn baler might cost you a lot in the long run?