If it is primarily the oil spots that you are concerned about you can use a detergent, as well as concrete cleaner, baking soda, or hydrogen peroxide to try to remove them. 

@Carrie Mims Aside from the challenges of actually getting a HELOC on an investment property (and especially now), I'd consider the refi for a few reasons.  1. to lock in historically low 30 year fixed debt. 2. to remove the lender entirely from the picture, so you can employ their money again to do another project. 3. to remove the loan variability (HELOCs adjust are generally interest only).

If they refuse to leave... you call the police and have them removed. 

Third be sure to check in with the park rules, some limit non resident owners, and some require older mobile homes to be removed between owners.

If a guest tries to over stay their welcome or is doing something stupid like blasting music from the hot tub at 3am.... you call the cops and have them removed.

Am I a good landlord because I didn't anticipate that a pandemic would cause the local, state, and federal governments to close most businesses and at the same time rewrite long standing laws to remove most protections of my property while at the same time requiring that all costs associated with maintaining that property, including taxes, continue to be paid?

The galley kitchen is pretty tight so we were planning on removing the cabinets on the opposite side and replacing it with something more space efficient. 

I just provided some food for thought.Also, keep in mind you'll have a very hard time finding financing for an investment property with only 10% down. 25% is usually the minimum.

removed the older MH and moved in a newer renovated one.

So short of total economic and social collapse where nothing will matter but guns and food and fuel, we have to play the game.