Bad credit home equity loan or line of credit.?

I’m in the process of buying a forclosure for aprox 1/3 of the tax value.
It is a cash only deal, the bank will not accecpt an offer based on a loan. The bad part is it will take almost all my money to buy it. And I have to build a garage for my work.
I want to take a loan out on the house, but I’m scared I won’t be able to.
The house is a two story home built in 88, the tax value is $117000
I need to borrow $30,000 to build my garage. I need to keep the payments low, so I want a 15 yr loan.
I’m not married yet, but could be if it will help the loan.
My credit is bad , my future wife has poor to fair credit.
I have put in for a loan for me and for me and my future wife as unmarried, on lending tree. With no luck at all! Does this mean we will not be able to get a loan?
It seems to me that any bank would love this offer, $30,000 on a home with $117k.
What would be the best way for me to get a loan, I have to get a loan or I can not buy the house. I have to have a large garage or I don’t make any money. Thanks
Ok my bad , I thought they would rather go off tax value since it is the lowest. I had it app last week for $134,000