Also, the concrete underneath probably needs treated ahead of time with a bonding adhesive. 

A soft spot is just a piece of the subfloor that has rotted over time for any number of reasons, including appliance leaks, window or roof leaks, or faulty plumbing.Ensure that you get a good look underneath the mobile home itself.

And the real mechanics underneath are very complex, but no, you do not win this game.

And I would probably look at the smaller houses where you can keep your unit costs down but still rent them at a higher price point relatively speaking. you are arguing one asset class. build a new hotel anywhere in America on any soil it's better than any apartment complex you can own. lower cost per sq ft than type 1 buildings and higher exit. we just ran into that and hotel is way better use after a rezoning application got declined for apartments. hotel is looking much better 

We have soil made up of mostly clay, rock, and some sand so digging footers or basement of any kind can dramatically drive up costs.

Cast iron waste lines become so tuberculated that waste can't pass through, or the joints fail and allow heavy root or soil intrusion.

For years, they’d used this site to stockpile soil from other projects, in lieu of moving it offsite (cost savings). 

For example, I’m doing three side by side duplexes and it’s costing me $135 psf, but I had to spend an extra $10k per foundation because of bad soil, and the smaller the property the higher the cost psfI’m working on a 28 unit with elevator, demo required, green roof, and it’ll cost me around the same psf as the duplexes.I’m doing three side by side triplexes which are full renovations, basement digout, all new facades, and that’s costing me about $106 psf for construction Non of these numbers include architecture, geotech, MEPS, environmental, utility plan, or finance costs

Offsets, root/soil intrusion and some build-up in the pipe.

Most engine lubricants contain lead and if handled improperly can contaminate the soil and thus allow lead to be tracked into the home.