I'm don't have near the expertise of many on this board in this business, but I'm old enough that I hope I've gained a little insight into life in general.
First off, let me congratulate you for having a work ethic at an early age. Way too many don't. Secondly, everyone wants to start at the top, but in reality, very, very few people do so. Most have to scrimp, save, and scratch their way to the top in their chosen field. Don't apologize for only having 8 accounts. If they are bid reasonably, and you are dependable, and do good work, you have a good foundation upon which to start.
I am not sure why you are considering selling your equipment from the information in your post, but I gathered that the partnership didn't work out, which is not all that uncommon. I have a suggestion. Rather than sell out and purchase what will probably be more expensive equipment, which you really don't need at this point, why not agree on a price for the equipment with your partner, and buy out his half? Doing so would keep you in the business with minjmal additional outlay. You might even be able to work out a payment schedule, or take over all the mowing right now, and pay him his half to retire the debt.
Best of luck. Neill
Dependable Mowing Service