NOI will not be affected by whether or not you have a mortgage. 

I'm looking for convention loan. 1 lender told me that per policy by Fannie Mae the required down payment for a single family home is 20% and duplex, triplex, 4plex is 25% down.

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.

For multifamily investments, using the LLC name is typically sufficient for legal and banking purposes, as advised by your CPA and banker.A DBA may be useful if you want a separate brand or manage multiple properties under different names, but it’s not required for most investors.

Quote from @Jackson Ebersole: Hi Piper,It's always smart to flip properties in-state, and I'd like to share some updated insights on why this approach is beneficial, especially in the New Jersey area.Lenders typically feel more comfortable with in-state flips because:You can manage the rehab more easilyYou have better knowledge of local real estate trends and valuesYou can respond quickly to issues or make decisions fasterThere's a lower risk of fraud or being taken advantage of by distant partnersI can help you with recommendations for the New Jersey market:North Bergen: Continues to show strong potential, with average profits now around $150,000 per flip and a gross ROI of 85%.Willingboro: While specific flip numbers aren't available, the market remains active with a gross ROI now averaging around 130%.Gloucester City: Still a top performer, with gross ROI hovering around 180-190%, though still on smaller profit margins.Irvington: Home values have continued to rise, with a 20% increase over the past two years.East Orange: Has seen steady growth, with home values up by about 16% since 2022.Paterson: Experienced a 14% increase in home values over the last two years.Additionally, Jersey City and Newark have emerged as promising markets for flips, with strong appreciation rates and growing demand.

I am not sure if she will move out by 9/30 either.  

We could sell that house by itself, but it would be sold under a land in common agreement and an HOA would need to be formed.I also confirmed with the Public Works department that a 2nd driveway can go in, with a septic designer that there's room for second septic tank, and with the public water company that they can tap into the main water line from one of the neighboring roads.I'm sure there are some more details that I would need to iron out that the code officer didn't bring up, but the high level answer I was looking for is that my town does allow selling off a second house under the LD 2003 legislation.

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.

The tenants debt is about $1600 and goes up by 10% every month because the property manager keeps the late fee. 

Start by reading the Ultimate Real Estate Investing Guide: https://www.biggerpockets.com/guides/ultimate-real-estate-investing-guide/introduction2.