Keep in mind you are only saving money if you can sell the equipment you buy at some point plus the true value of the hay you used is less than what you would have you paid had you just bought hay to start with then you have saved money. And you need to compare apples to apples. In other words top quality hay brings premium pricing while fields people usually give you for free do not so when you use the pencil compare equal product.
That all said you can likely bale with your little tractor (if you pick the right baler). A New Holland 65 compact would be my baler of choice. I run one with my Kubota
L285 compact tractor (26.4 max PTO hp) but closer to 23 hp with the throttle set for 540 PTO rpm. My baler is a 1960 model so it is 55 years old. All my other equipment is antiquated cheap junk. You will need to drop them on the ground with a small tractor. That all said, I like doing the hay (been doing it since 2008), but I have yet to make the first dollar and I literally have peanuts invested in all my equipment and the tractor too for that matter.
You will read stories on here of guys with $25k tractors, $10k balers, $10K cutters, new trailers, grapples, etc. then going out baling a measly few acres of weed fields and they will try to convince you they making money. It is not going to happen. You can not outrun depreciation on the equipment, interest you may be paying on a loan, or interest you are also losing on an investment if you pull cash from investment by baling a few acres of weed hay using expensive equipment.
Try to cover massive amounts of acreage with your little tractor and it will likely then not hold up as it is not really the proper tool for that job.
Big time farmers can justify that modern expensive equipment but they going to have to cover the acres with it to make it pay. A small timer is going to have to buy old, cheap, low hp stuff, plus do it the 1950's manual way to have any hopes of making money on a small time hay operation. Regardless you will be working for free and tinkering on the old stuff quite a bit to make it functional and you will do well to break even. If you like that sort of thing (I do for for some masochistic reason) then it certainly can be mentally rewarding but not really financially rewarding.
Your money would be much better off in an investment portfolio....