Sounds like you have been getting a lot of good answers here, but I will add my two cents here. Make sure you get a subscription to Lancaster Farming. It is the bible of sales and suppliers in PA, NY, MD, OH. If you cannot find stuff in that paper you do not need it. They do have a web site,
Lancaster Farming: Ephrata, PA | Lancaster Farming
There are only two kinds of tractors to consider IH and JD. Look around at the farms in your area and do a quick head count, and you will see that red and green are the vast majority. This is for a reason, they hold up the best and PARTS ARE AVAILABLE! You may have to know where to look, but you can always find what you need, some new and some used. Example, Bates out in Ohio does strictly IH parts, and there is such a demand for some old parts and castings that they have started making them new again.
Now lets talk about tractor design and maintenance. Every JD model is distinct when you are talking anything of size. Their 20, 30, and 40 series utilities share a basic trans and rear (twin stick, 8 speed, with park gear), but bigger tractor say 3020, 4020 etc drive lines are unique to each. IH on the other hand has a clutch back design that is identical for the 06, 26, 56, and 66 series, until you get up into the bigger ones like the 1466 where things like the brakes do change and the basic trans changes also, but you will not want anything that big. JD internalizes many of the major service items, and IH has external access. Example PTO rebuild, with a 4020 you will split the tractor, with a 966 you pull the pto out the back and you can have it done in hours instead of days. Brakes are another example, JD remove rear wheel and axle shafts to get to brakes and spend 500 a side in Parts, IH, remove 6 bolts and spend 100 in parts and your done.
Sizing of tractors, to pull a discbine especially on hill, 100HP is what you really need to get the job done safely. I pulled my 9' discbine with 80HP and it was too slow and heated up when I tried to push it. Now I pull with a 100 turned up to around 125HP and I have actually pulled it at 10mph (did not do for long, just did to see if I could and it worked well, cut was good and that was 110 bale to the acre first cut)
Rotary rakes and star tedders are the only way to go, period end of story! Wire wheel rakes are cheap for a reason, they pick up green material into the dry hay unless you are working on completely level ground. Use a rotary rake once and you will never go back. Rotarys stand the hay up and really do a great job.
Balers, Green or Red(NH), either is fine. I run around 20K through two 336's. They are fine balers, if you know how to run them. Like all bales they have their best operating procedures. 346 has a wider pick up and usually go for 1-2 K more than a 336. I have baled up to 200 an hour with a 336 with people on the wagon and I could stay in the seat and keep moving the whole time. Your speed with a baler is not determined by how fast your ground speed is, but rather how many bales are coming out the back. Usually doing 200 an hour is in first gear about as slow a ground speed as I can run, but the rows were thick and the hay was nice. Round bales do not save much time over squares, but take less people to do, and all is done from a tractor seat. Rounds can be stored outside, but keep them off the gound with pallets, and cover in good tarps, but keep ends open for ventilation. Harbor Freight has some nice hay tarps that work very well. They are designed to stacking as a 6 bale triangle and as long as you need. Run the tie down ropes on top of the skid in the spaces, and then run plastic pipe down through the loops on the tarps and tie down on every bales or 3' or so.
Most importantly, DO NOT BORROW ANY MONEY! The price of milk is extremely volatile, and there will be many times you may have enough to live on, but not make equipment payments. Good luck.