so if I start with 3.5 i'm good to go?
You need to understand the math before you give people millions of dollars.
If the loan is "interest only" then 7% means that for every dollar you lend, the borrower will owe you 7 cents per year. So if you lend out 3.5mm, the borrower will owe you a yearly amount of 3.5mm times 7% (3,500,000 x .07) which is 245k. If you split that between 12 months, you get 20,416 a month.
There are usually fees that borrowers charge with these types of loans that can generate additional income.