This one isn't really that tough of a call. The distance and size of the account would lead me to pass on the idea. I was in a similar situation a few years ago. The only difference is it was spread out over 40 accounts and it required an investment of $25k. I went from 10 or so accounts part time to 50 accounts overnight. I quit my $50k/yr job (family w/ 2 kids), wrote a $25k check, and became a full time lawncare business owner. Every person I knew said I was crazy. I worked my ass off the first year!!! 7 days a week for 5 months. No joke. I remember telling my wife in August that I honestly didnt think I could make it to winter. I almost balled like a baby I was so exhausted.
2 years later I hired my first employee. I spent another $35k to acquire another business at which everyone said I spent too much and their was no value in it. Again, contrary to their opinion I made it work. I built the business into a full service company and now I am focusing 100% on fertilizer applications. I am in the process of selling all of my maintenance business to a local competitor for $140k including about $40k in equipment. I guarantee people are telling him he's crazy for buying it and I have people telling me I'm crazy for selling. The point is, nobody knows your work ethic or drive and nobody knows how you plan to grow. I would say that this particular opportunity seems like a lot of resources focused in one location and I would make damn sure you can grow immediately in other areas if you decide to take the plunge. Be ready for naysayers and those waiting for you to fail. There will be a hundred people eager to watch you fail and nobody to lift you up once you succeed.
Good luck and I hope it works out for you if you take the opportunity.