Congrats on the accounts, good work!!
If you are confident that the Deere can last a season or 2, then you have a solid 38" mower already -MAYBE I would pick up a used 48 or 52" WB, depends on how many more you pick up-- At your rate you may be one of those 40-50 account newbies by Spring! But if your solo and the Deere runs well, and you have some money to invest, I might start looking into a good deal on a used 350-550 range dump truck. You have some time so you could catch a good deal if research. An enclosed trailer is the way to go, and 16' is nice. I have a similar setup to yours and I only have a 12' enclosed. If you organize things (racks etc.) the stuff you have now will easily fit. 14' is good too.
I guess my point is that if you have 10K to spend, a dump truck ($6-8K) and an enclosed trailer (14' = $2K) will carry you and all your current equipment plus some material to the job with no added overhead, and at the rate which you are marketing, you can pick up another mower during or after the season. Plus you'll better know what size you should get.
Again, this is just how my mind works so do what you feel is right, but I think for you, a dump is a money maker!!!
Damn I wish I had $10K!!!!!