Be smart, if you were farming you wouldn't put your only seeds in questionable soil; Reap what you sow...

To date I've had 1. the plug of a window air conditioner eaten by a large puppy that resembled an elephant, 2. a porch swing partially consumed by the same galoot,  3. flower beds totally destroyed because the dirt is, oh so cool to lay in in the summertime,  4. a carpet scratched down to the subfloor underneath by a dog left in a bedroom and either bored or going through a panic,  5. 

Having this area of moist soil is an all out invitation to termites and other critters as well.

I place R-19 batts underneath then covered by "aluminized belly-wrap." 

The property I recently acquired has two feral cats living underneath it. 

Pour a little down each sink and look underneath.  

If it is next to a ditch or small stream then it may have floodplain over it.That may not be the answer you were looking for because "Is it buildable" means different things to different people and to me I look at everything including; easements, soil conditions, wetlands, utilities, storm water drainage, etc.

The purchase agreement should layout a time frame to complete some of these "due diligence" items.You will need a boundary survey and title commitment to verify there are no liens or encumberances on the property.You will want to hire a geotechnical engineer to verify the soil is suitable for building an apartment building.You will need an environmental engineer to make sure there are no contaminants (asbestos, mercury, lead, etc.) on the site, as well as wetlands and/or endagered speices.If you need to rezone the property we may want to consult an attorney and/or civil engineer to help with that.Depending on how many units you intend to build the city may require a traffic study be completed to determine the impacts to the streets and intersections.This is typically how we start a new site and it is a very general list of items.

@arturo grading is moving and sloping the soil/dirt around a site away from the house or building to get final grade per plans.

However, here is what I have learned on it now:After speaking with Health Department and Soil Engineers, it looks like I can keep the septic issues to just maintenance.