I'd need the interest rate to be roughly 5% to breakeven on an interest-only loan, and was considering a balloon payment in 5-7 years.

Like I mentioned to Eliott, I'm very young and I can't get a loan.

To fund your next deal, explore conventional loans (15-25% down), FHA loans (3.5% down for house hacking), DSCR loans (based on rental income), or HELOC/cash-out refinance if you have equity.

Quote from @Beth Johnson: We pass all loan servicing charges through to the borrower including set-up fee, monthly fees, and any servicing charges such as payoff demand generation, and loan close out fees. 

What loan size and loan to value?

You can open a Self-Directed IRA and use the IRA funds to buy a house using a Non-recourse loan. 

If a HELOC isn't an option due to Texas laws, you could consider a cash-out refinance with another property or a portfolio loan, even if you want to keep your current rate.

Hello all,
I'm looking to buy my first multi-family. I have a large lump sum saved in an investment account for down-payment and any additional costs. I currently have no debt and make under $100k a year. Because of ...

Unlike a mortgage the interest on your loan will not be tax deductible.

If you close with a conventional loan, it will need to be in your personal name.