but first,  seek for mentors who are not promoting their mentor ship program, who are trying to make money and may not care about your well-being.

Once I retire in a week, and get the 457 money, it will give me roughly 80% of the down payment.I'll probably use a bit of my existing HELOC to get the rest of the down payment.I could ask my credit union about increasing my HELOC so I could use that to cover all of the down payment. 

It's basically insurance to cover the lender for the risk of making a loan to you.

If your down payment isn't enough they make you take out a second personal loan at something like 10% interest to cover the difference.

Could the payment be covered ?

Ask for a cost reduction that will cover some of the work, maybe $1k?

It was gutted by fire, holes in the roof, covered in junk, condemned, etc. 

Also, you have to make sure you have the reserves in the IRA to cover much of the expenses.

I'm currently looking into house hacking combined with rehab using a loan like Homestyle that will also cover rehab costs.

When I bought it someone had hit a brick wall with a truck and the resulting hole was covered by plywood.