You say that you "get" their other work. Does this mean that you get paid to do the other work or you do the other work for free for the "right" to be able to do hay on their property?
Other way around. I have these customers that I cut non-hayed areas for. Their properties were also in disrepair and I fixed them up. I asked about who was cutting their hay and they would shake their heads because they didn't like who was doing it. I asked them if they'd be interested in me doing it, and they appeared to be very interested. One guy was receiving nothing from the guy who was cutting his 24 acres. The guy would take the hay and leave a mess. I was under the impression you gave the property owner a small cut of the profit, or some hay for their horses/cattle if they owned any.

Do you have to produce hay, or do they just want it to be kept clean and neat?
How much land are we talking about here?
It varies from customer to customer. One is disatisfied with current hay guy. One is paying me to cut 20+ of which about 12 could be hay with a little weed spraying. The 3rd wants some of the hay for their horses for the privelage of letting me keep the rest.
Total between the 3 is about 39 acres. (1 is 20, 1 is 12 and one is 7).
I could get more without too much trouble.
I guess my quandry is: Do I spend $12,000 on equipment to cut hay without anything more than a small barn to store it and not a ton of experience? (All I have done is handle/transport bales). have lots of common sense & mechanical ability. I would have no problem tarping it out in fields until I sell it, but not sure if that's adviseable.
One of my "rich guy" customers may be interested in building a simple hay pole barn. I am pretty sure he'd let me bring hay to his property to store anything beyond what I harvest off his property if he built the barn.
I own no livestock. I would simply like to be involved in cutting/selling hay, but have nothing bother than a rough idea of what I would make per acre, bale in gross profit.
I think it's a great way to keep myself in front of wealthy land owners that need lots of services.