You can ask the Sub's, or whoever you are going to do the work, which materials they need and price them out at other supply houses.

I was concerned because the tenant has roofing supplies all over the back yard in addition to a trailer and roofing machine in the street. 

Plus the resources Africa supplies.  

I have done wholesaling in the past (not in RE, but in reverse supply chain liquidation), and had to deal with a lot of unethical and dishonest sellers.

At the time I didn't really understand why, since you had to pass the income and credit checks regardless and there were only 2 companies that owned all the upscale places so not a huge supply.       

Lot of new-co that gets grabbed by investors which adds supply.

In terms of new construction, a couple things to be aware of in San Luis Obispo County are water shortage issues and development fees/taxes which can significantly increase the building costs.SLO city and the neighboring cities are particularly diligent on their water usage, as most of the county's water supply comes from three surface water reservoirs and a groundwater basin.

It seems that good, decent, qualified tenants have the pick of the litter, often flaky and uncommitted when there is so much supply out there. 

Cape Coral also offers a great supply of homes that are not in flood zones and otherwise have low storm risk, particularly with some newer buildsIn terms of cash flow, single family in general is not going to be the best bet for optimizing that focus.

I can see where a lot of supply would temporarily disappear if they rent instead of sell ... still a motivated seller, so those units are likely to hit the market in the future.