Except for the two bedrooms, I took every room down to the studs = new wiring, plumbing, insulation, drywall, flooring, fixtures, counters, doors, trim, windows, appliances, roof, gutters, landscaping, fence).

Make sure door sweeps are on external doors, make sure there are no gaps round the doors, make sure all holes eg plumbing fixtures under sinks are sealed, pipes going through walls are foamed up to seal, and so forth.

Mold is caused by water.. you have to stop the cause of the water which is usually pretty easy to do if it's a leaking pipe or a busted roof.

Especially the days when you discover that big capex like a roof being blow off (happened 2 years ago), some tweakers climbed up on the roof and gutted the A/C (did two of those in the last 12 months), an evap cooler leaked for so long that the drywall on the ceiling of the kids bedroom caved in (last year), the hot water heater blew a hose and a major leak went unnoticed for 10 hours flooding the hall, kitchen and living room (dealing with that now), the tenant smelled gas outside, the gas company came and shut off the gas because the underground pipe is corroded AND also discovered that the water heater is not venting properly so it got red tagged (just dealt with that last month) or the time the tenant "invited" a homeless guy over, he moved in, then called his other homeless buddy up and he parked his crappy RV with his entire family living in it in the driveway.

some ideas: New counter-tops, paint or replace cabinets, new flooring, etc.  

My second tip for you is that you familiarize yourself with current bid, bid deposit, bid increment, and counter bid.

They counter offered and surprisingly they were fine with that price.

75 - 300 / sq' , i couldn't tell you, are you building a storage shed or a house with quartz or granite counter tops, marble floors in foyer / baths and decorative tiles in the baths, stained hardwood trim, custom kitchen and decorative trim throughout the house ?

At least you'll be getting some peace of mind along with some new pipes. :)

I countered that out and just encourage the seller that i won't be crazy but will ask for normal things to be repaired.