That's what we do; make them all jointly and severally liable for the rent to be paid.

You can do it as a joint venture where you partner will also likely sign and guarantee on the debt, or you can have an investor provide you debt.  

Immediately adding capital improvements.

Flipping houses seems ideal since I worked in home improvements for 5 years, including owning a construction company as a general contractor at one point.I never initially invested in a multifamily because, in my area, they are all in bad areas.

Check your credit scores online - see if there's things you can do to improve them. 

I've read that the interest from the cash out refi mortgage is NOT tax deductible UNLESS it is used for improvements for the home.

Here are few questions that come to mind..What kind of improvements/renovations did you make while you were actually living in the home?

Joint venturing and partnering with successful individuals can be a powerful strategy.

This is my first house hack and never dealt with this situation, and don't want to incur with any other expense from beginning when I could be using this money towards improving the rental unit.

Probably improving, but some tough areas not far away.