My company borrows money in first position at 9% interest only all the time. Its a number we can make cashflow in our market of Kansas City and is also a very solid return for the investor.
We always put our investors in 1st position and give them a guarantee against the rest of our company and make them an additional insurer in case there is an insurance claim. 9% return is a legitimate number for an investor to make work in a cashflow market, but the big thing to consider is if they will be able to make a margin on top of your return and what you will get if things go wrong.
Having some extra equity on top of your loan is very helpful, but having a guarantee against other assets in my opinion is more important. My reasoning is that if a tenant trashes the unit so much that the property is worth less than your loan, or something else hurts the value it's tempting for the owner to just stop making payments and let you foreclose. Hopefully the person your working with would want to protect the relationship but it sets up a bad incentive in that type of situation without the extra guarentee which is why we always guarantee our loans against all our companies assets.