We got a HELOC on the house and used it to build a garage, fix up the kitchen, new paint and fixtures throughout the house, landscaping and I acid stained the basement floors to give it a one off look.

Other reactions may create formic acid, another irritant.

Our house was built with the old, softer "M" grade copper plumbing and the slightly acidic water was slowly dissolving the pipes, causing a blue-green staining in the tub. 

How do you feel about massive amounts of acid whey dumped by Byrne Dairy into Cortland's watershed?

Power wash the floor , let degreased sit on the oil spots for a while , then clean with muratic acid , then rinse again .then paint .

Any recommendations on cleaing this sandstone fireplace.I figured I'd hit BP up before trying sulfuric acid and all the safety gear required to do that.

Jane- I know you're new to development, and its far reaching- but if you wanted an additional source of capital for financing the ground,curb,paving,storm,sewer, etc- you could create a CID (Community improvement district) to assist in this.

Any remaining residue can likely be scrubbed off, or removed with a dilute mix of muriatic acid and water. 

@Robert Perry with a muratic acid and a jetter you may get through it.

A very quick acid test is monthly rent to purchase ratio. .00765.