if you're just starting up, look for a GOOD belt drive walk behind. They're very versatile, can cover decent ground, come in various sizes, are affordable, and really easy to fix. If you wanted to, you could get a hydro WB for more $. Another option is to get a GOOD used zrt. I got a 36" belt WB and a used 52" ztr last year when I started. Now, come Jan, I'll be getting a brand new Tiger Cat or Turf Tiger to replace my current ztr. So i made enough in my first year, just starting out, to justify the cost of a new machine. You could do what I did, and try it out on the cheap first to see if you can make it. OR give it hell right form the start, go balls out and drop the $ on a brand new machine. You just need to be able to get the accounts to cover the cost. That's the hard part. Start getting accounts NOW, that way you have an idea if you outta go new or used. You can get a mower pretty quickly if you need to. So get the accounts first, then get the machine.
also, skip the JD and get a Scag. I'm pricing Tiger Cat's now with a 61" Velocity deck and 27hp Kawi. lowest I was quoted was around 8,000. thats brand new. 0% for 48 months. 2 year commercial warranty, 3 year deck and spindle warranty. Both my current mowers are used Scags, high hours, rode hard and put away wet and they still run and cut great. Good luck.