Is someone actually saying to use home equity? Where are you getting these numbers from? If the rental house is meant to pay for college and it’s paying out 30k then look for schools that are in that range (or 35k if you add in a federal loan for your son). My average by college confidential standards kid had schools under that cost.
I’m also confused about your primary residence. No fafsa only school will consider your home as an asset.
You sound like you have good income and as others have said, that just means using a different strategy to find colleges that are affordable for you.