do they just knock out the concrete slab and create a crawl space?   

Once you break ground you will have a few weeks of delays through the life of the build....concrete, inspectors, weather, etc.

We just closed, so no concrete outcome, yet.

As long as it doesn't go over the height limit and isnt filled with concrete, its flat fee.  

Nail polish remover also works well for permanent marker.

Here's the problem, there is no footing underneath the existing concrete slap of the enclosed porch.

Most come off with mineral spirits and scrapingMy question:  has anyone used a shoe polish, or can recommend to me a coloring substance to repair floor!

I had several rugs in one property hiding stuff (sun bleached hardwood floor with a rectangle where that rug was, garage concrete cracks.)

I have carpentry and plumbing experience but moving to an area where the structures are primarily concrete walls so I’m especially interested in how that might change the order and tactics of the rehab flow.  

It's not worth the hassle to defend yourself if they question an invoice from you, where they may not from a contractor.Also, you may instead want to look at enzyme based concrete treatments over paint.