Based on your last post, it appears you don't have a maintenance tech budgeted. I know lots of owners (and PM's) that feel 100 is about the max for a single manager, so I think you're fine with that. I know others disagree. Our manager runs 106 units by herself, and its a C class with low income tenants. It works fine. One maintenance guy should work with a 90's complex, but again, having options for help when needed would be critical. We have one, but also contract out a lot of make ready work. But you WILL need at least 1 full time maintenance person, and it doesn't look like thats in there. Some of your $60,000 R&M is probably part of it, but not sure it would cover a full salary.
I know Brian and Ben disagree, but I think economic vacancy really depends on the area. They have far more experience than I do, and I ONLY have knowledge of my own area, so keep that in mind. Our c class property runs about 7% economic loss to include bad debt, loss to lease, physical vacancy, etc. There's just such high demand that even if someone skips or gets evicted, there are people waiting to get in. I don't project that number going forward, as things will likely change with new construction, jobs, wages, etc. We projected 12% after stabilization, and its running 5-7%.
On the other hand, if its currently only 86% phys occupancy, then assuming 15% is risky. If there are other properties in the area, find out how they are doing. If you find out that they stay full all the time, then its probably a management issue with yours and 15% may be safe. If they only stay 86% full, then 15% is not safe.
The MOST important thing is going to be your management company. Make sure they have experience with the demographic you're buying, and that you're going to get the amount of attention you need being in a smaller town.
Make sure you're budgeting for property taxes to go up based on your purchase price.