And of course, both tenants deny ever putting anything down the drains.

You’d still need to confirm water sources and drain. 

My contractor sealed the holes, unclogged the weep holes, removed dead landscaping that was piled high around the house, and installed a French drain and gutters, all of which we hope will solve the problem.

One drafted by an attorney stands a better chance at garnering a response but even that appears to be money down the drain.

I've seen extensive foundation repairs done to cinder block walls that are bowing from external hydraulic pressure, and they've been repaired with extensive steel beams, tension systems and a drain cut in for around $12,000.4" is a fair bit of slope and to put in floor leveler...well, that's a lot of floor leveler.  

They will take the floor out down to the footing, rework all the drains in the building, install drain tile on the inside of the foundation that drains to a sump.

The purchase price is $626k, with one unit delivered vacant, unit two currently paying $800 a month, and unit three paying $700 a month.My question pertains to the inspection report I have received, which states that the roof has around 5 years left, and I need to replace the drain iron plumbing to the street, which is estimated to be a $10k job.

. $15,000 down the drain that could have been used towards the down payment on another property.

have 3 kids though, little drains on my account ;) lol...  

Most of our tenants are reasonable folks, and the buildings in A and B level communities have mostly routine issues (leaky drains, roofs, etc).