Have been doing this for a few years and there has been lengthy dry spells like this month.

Is it the risk of environmental cleanup liability if there's soil or groundwater contamination?

Other areas were your relying on Wells that are very expensive and or you pay 15k for a dry hole.. etc etc. there is basic due diligence that needs to be done and relying on someone else to do that for you is frankly foolish.

Perform due diligence, including soil tests, environmental assessments, and surveys to ensure the land is suitable for construction.

You dig a dry well do you know how deep you can dig into the water?

The leak was pretty severe and ended up going into the garage, so we had to dry out and ventilate the garage as well. 

This gives you the dry powder you need if a good deal comes along or unexpected expenses and you keep the existing low mortgage rates and do not increase your payment until you use the HELOC.Consider how you could increase the cash flow on the existing properties and if you have the means to pay off one of the houses to increase the monthly cash flow that way.

MAKING SURE THE SOIL IS TESTED TO MAKE SURE IT CAN STAND THE PRESSURE I ASSUME, LAYING THE SLAB OF CONCRETE KEEPING IN MIND OF UTILITIES AND ETC.

My old sources recently ran dry and I had to venture out.

Is market like Texas where they often have soil/foundation issues, or like MN/the Midwest where the asphalt shingles might have hail damage?