I immediately started cleaning up the place, there were cobwebs everywhere and the place smelled really bad due to urine soiled carpet throughout.

All investors need to learn the GIS and other mapping applications intimately, the overlays show things like Zoning, Flood maps, Soil types, Topo, and much much more, all at your finger tips 24/7 I never take anyone's word for anything, especially from a government office, even before the GIS  was wide spread I would go to the county offices and read the maps myself,  Do your own homework and dont rely on others,  same reason I learned abstracting, understanding more than most will get you farther than most, best of luck.

Just kidding, I’m selling a lot right now and the buyer asked for the following contingencies:1) that the HOA CC&Rs don’t change during the closing (seems very unlikely to me)2) that the lot is a legal buildable lot (I’m ok with it because I check this during my due diligence phase when I buy it, and honestly he should confirm this before putting it under contract, but it doesn’t bother me because I already know that it is)3) that the property passes a perc test (this means that the soil is acceptable to sustain a septic system, again I’m ok with this based on my due diligence I can’t foresee it not passing a perc test, and it’s a reasonable request from a buyer.

An area where the soil is very compact? 

they can test the soil for drainage quality for the septic system. 

@Sandy Preston, this might be obvious- I understand that you want a HELOC on your 100% owned rental property.

Foundation companies are in every neighborhood daily - but many homeowners/investors have found that there are many anchoring options that are effective as long as the drainage/soil are addressed first. 

As for areas to relocate to...I'd check out Parrot Mountain outside of Sherwood, Yamhill county, or east of Portland out towards Estacada/Sandy/Damascus/Mt.

These chemicals and pesticides leach into our soils and water along with drifting over in the air for miles. 

Sandy ground is going to require digging, unknown buried utilities will also require digging.