I’m torn between fha financing with 3.5% down, or 20% down conventional.

In that world, they don't generally do a "Pre-Qualification" like they do on a personal, conventional mortgage.

Bought it with a conventional loan 20% down.

I'm a wealth of knowledge on the conventional lending side if anyone has questions.Alberto 

I currently have 10 Conventional mortgages and I was told that is the maximum Fannie Mae allows; so the big banks are not able to finance any new purchase.

If you are worried about keeping up with your current plan for rentals, there are plenty of alternative options outside of conventional lending (private lending or hard money loans, etc) that may work for you.

Purchase price: $125,000 Cash invested: $3,500 Sale price: $125,000 Single Family home I bought with a conventional loan with 3.5% down.

I was able to obtain a preapproval for convention on any investment property using a mortgage broker at 4% but was wondering if it would be bad to try applying for a few more preapprovals with different banks to see who can give me the best rate for conventional?

I used conventional loan with my bank that offers 2nd home financing.

Are they able to obtain conventional financing?