Clearly you will need to raise the $500k privately given your current credit situation.

I don't even know if I can qualify for more via FHA, I think I might qualify for like 455k based on all the numbers... do you think I have a poor chance of getting this fourplex? 

Assuming you have equity and you qualify for a conventional Fannie/Freddie loan then yes you can.You should also call the small local banks and credit unions in your area as they can be more competitive.

He wants to pay for the whole year rent if his credit report comes back blank.

I've rented to a lot of tenants with bad credit.

This is in NJ.I spoke to someone from Andrews Credit Union who is offering 95% LTV HELOC but the banker is unsure if the underwriter will accept a duplex.

when we would log over a timber track sell the track to a new owner who was looking to build but needed a year or two to get permitted house sold  etc etc but would buy from us on terms then we hypothecate the note.. but we owned the dirt free and clear .. and to do this you needed stellar credit and balance sheet .. banks were just not going to make loans because you had a note  LOL.. 

I have good credit 750+.Thanks for the help!!

Is this the best way to use funds to appeal to more buyers, or leave it as is and offer credit.

I am looking to complete a large rehab this summer and have poor success with contractors in the past.