I improved the bathroom surfaces.

The terms can be pretty much whatever you can agree on.A couple pros for the seller you can use to help improve terms are: 1.

They might go up if you materially improve the property or a sale may trigger a new appraisal, but that's all part of the game.

To make a long story short, I am using my rental income to purchase a new home that we will be living in and was prequalified with no issues (mortgage company hired third party firm to look at my rental income and returns to qualify my income, I gave them every document on earth, leases, taxes, insurance, mortgages, etc...) and then underwriting says no due to the fact that the last 2 years of tax returns (2017, 2018) I reinvested all my money into my rentals and they are deducting all that out of my income, ie. depreciation, capital improvements, supplies, repairs, utilities, maintenance etc... 

@Greg DickersonIf I were to get a hard money loan for say 750k for purchase, and the value of the building is more with some improvements, could I do a cash out refinance through a bank for the new, higher, appraised value?

I just have a lot of equity in my home from the improvements and I would like to pull that equity out and pay off the personal loan I used to help with the remodel. 

You have to purchase it and then substantially improve it to qualify. 

Depending on what's hurting your credit (you said not good), sometimes there are strategies to easily improve it, sometimes significantly which will allow you to get your own gap funding.

(adding 2 floors complete re-purpose) The builder claims that the improvements will more than make up for the poor cash flow by improving the value of the property substantially.

Assuming that the market and neighborhood where the property is located is steadily improving.