Year one accounts for me was about a dozen. Seems wimpy I know, but I had no experience and did not market heavily that year. To me, was better to learn doing a few then botch a whole bunch. You won't have that issue.
If you have a bunch of existing contacts who want your services right now, I would think 50-60 accounts would be doable perhaps. If you are starting from pure scratch, not quite that many.
7x14 Stealth SE Enclosed with 48" side ramp
2013 Gravely Pro Turn 260 with Kohler 26.5 EFI
08 Toro Z400 48" deck, 21HP Kaw with EZ Vac twin bag
09 Exmark Turf Tracer HP 36"
21" Toro SR4 Super Recycler
Stihl KM90 Kombi w/ straight shaft trimmer & tiller heads
2 Husqvarna 125B Blowers
Turfco XT5 Aerator
Turfco LS-22 Overseeder
EcoLawn 200 Applicator
I can do all things through Him who gives me strength.