I don't see a ton of external issues cropping up in 6 months.

The only problem with an app is that construction cost vary so much based on different factors.

I suspect that other factors in your financial profile will play into the answer.  

Some local investors tell me no less than 8% vacancy factor and cap ex depends on current conditions of the property and what will need to be done within the next 3 years, could be 10% of gross rents.

If you plan to invest out of state, remember to factor in management costs.

I don't see that you factored anything for that either.

Obvously other factors play in and the property is a big variable.  

What economic factors must be present to carry on business in our economy, land or Fords?

This is also with me factoring in 11% for property management, however, I plan on managing this one myself.

I typically use ARV = pro forma NOI/market cap rate.Be careful with this as there are many factors affecting this number.