Ten times the houses means ten times the roofs, ten times the furnaces, ten times the fridges, etc.

But neither can be accurate if they don't take into account the floor plan, condition of the mechanicals (electric, plumbing, HVAC) and structure (roof, gutters/drainage system, foundation, doors, windows, walls, woodwork, special features) and furnishings (cabinetry, floor coverings, window coverings, appliances, lighting fixtures, plumbing fixtures) and land (zoning, location, yard size, landscaping, fencing, nearby attractions/distractions).

A bad roof will affect value or something else major like a cracked foundation but not paint colors or window coverings etc.)However, it is my experience that Hard Money Lenders always appraise a property far lower than what it would sell for.

If you're repairing a hole in the roof you're not adding life to the entire roof, just repairing the whole. 

And he likes to barter dental work for other services (house painting, roof fixing, tree trimming, etc). 

Roof has a hole in it.

That does not consider your AC, appliances, hot water heater, and maybe roof will all need replaced within that time frame.

The points rack up.

One guideline I use says that if the rent is $1000/mo, then the most I can pay for that rental (including any renovation) is $80,000.One caveat though - if you purchased that $80K property and it had plenty of deferred maintenance (needs a roof, windows don't work properly, old HVAC, galvanized plumbing), then you would need to have these items fixed prior to purchase or factor in this maintenance (pay me now or pay me later...).  

@James Rodgers I hope so I'm getting in touch with GC's at the moment to get multiple bids on everything from roofing and tree removal to a general overhaul on the inside.