My concern is that if i apply for a HELOC to use for the down payment before i apply for a mortgage, A) I wont get approved due to my DTI ratio, and B) I wont get approved without first showing the bank I have the 20% down payment before pulling the HELOC.

I got pre-approved by my previous lender and by another lender.

If the seller accepts the offer, (contingent on appraisal[as per court approval requirement]), How should i proceed in the situation.

When offers come in, prioritize pre-approved or cash buyers for a faster closing process, negotiating where needed to maximize your profit.Finally, conduct a post-sale analysis to evaluate your financials, noting how actual costs, timelines, and profits compared to your initial projections.

You could always put something in the lease that allows them with permission and approval of your insurance.

You should keep saving, get pre-approved so you know where you stand, and start working with an investor-friendly agent to show you homes so you get some reps in.

Your engineer should be able to approve some options to fix, then have companies quote to the engineers specs.

In your experience, how quickly do the insurance companies approve these for the family?

Do you want to build it to code and get it approved by the county? 

What exactly would make a city board approve non-affordable (i.e. not Section 8)  apartments?