@Jimmy Rojas..Full disclosure, I'm a mortgage broker in CA + AZ. 

CrossCountry Mortgage How did you add value to the deal?

You can transform a space that you merely use for storage into a cash-flowing rental to subsidize your mortgage, your bills and other household expenses.My journey to house hackingIn Spring 2022, my neighbor mentioned he had started renting out the Accessory Dwelling Unit (ADU) on his property on AirBNB.

(beware of private consultants that you have to pay.) 

Conventional mortgages require higher FICO, reserves (money set aside to pay the loan), tax returns...just on that note, they typically won't count any income from the property rents until that money hits your tax returns for 2 years. 

They are two completely different loans with different qualifying criteria so it would be best to speak with a mortgage advisor well versed in both to see which structure would fit your needs. 

I’m wondering if I should let this block me from getting any tenants in the units before I take this project on because it’s tough to come up with the mortgage with no rents.

Also, there is IRS publication 527 (p527) Residential Rental Property.Otherwise in short, your rent less your expenses (generally mortgage interest, insurance, taxes, repairs) and less depreciation is your profit/loss for federal purposes. 

If you buy a house in full, or get a mortgage with the intent of it being a rental investment, is that number tax deductible, and are the renovation costs?

Following on the previous poster, we did use hard money to fix and flip, also regular mortgages before I learned how costly they are for short term loans in closing costs (coming and going), and then DSCR mortgages that do not report to personal for LTRs and STRs.