Spray a mixture of vinegar, hydrogen peroxide and dishwashing liquid over the floors.

IF its a rental I would use the rustolium epoxy to spray on. 

Now, if you are in a rental situation where there is continuity between all the rooms already and you are looking for the next level of pizzazz, you can update old laminate counter tops with new laminate counter tops, lay vinyl plank flooring in the kitchen and bath, spend a little more on bath and kitchen light fixtures, add a few USB charging outlets, install ceiling fans in bedrooms instead of flush mount fixtures (but remember, more moving parts means more points of failure which can equal more maintenance calls - however if you are getting better tenants and higher rent, maybe that doesn't matter - I personally try to remove points of failure - spray hose from sink, ice maker from freezer, garbage disposal, really anything having to do with water).

Having it sprayed shouldn't eat up your profits

I sprayed the entire house (including the floors) and that got rid of the odor.  

When I trash out a project I look for those guys driving a truck with plywood sides built 10ft up spray painted with the words "trash pickup"  Or "free appliance pickup"  usually you can negotiate a great deal with those guys =)  

Exterminators can not spray up into appliances and that is where they nest.

He tells how he bought this sunscreen spray, but he didn't know he should've spread it with his hands, not just spray it.

Also, can I spray the Bioshield decontaminant myself to get rid of the droppings?

I spray preemergent weed killer, apply fertilizer.