When running numbers to buy a place, I plug in$5,000.00 per unit to separate.

Are you looking to get an investment property at 20% down or a primary residence you can house hack (rent the rooms in the house you are living in), or a primary residence (better for people who are married/have kids/don't want roommates) where you live in it for 12 months then rent it when you buy your next property to repeat the process.

In my experience, and the experience of hundreds of professional property managers I network with, counting the late fee as "extra income" will come back to bite you.

BUT, if I could potentially get the seller to buy down my interest rate in closing, that could increase my ROI to just over 11% and increase monthly cashflow by ~$45.Thoughts?

You fail small.If it has extra land, then it can be a great deal, if the market needs more. 

Unless you own the house cash, in addition to the advice you've received, you can't just transfer a house from personal to an LLC without risking the option of the loan being called since the LLC does not have two years of tax returns.For new investors without cash to buy, LLCs are about the biggest cause of analysis paralysis out there.

If anyone has any extra tips, I will gladly take them all!

However, since we don't have any experience in rentals, we don't know if we should buy a single home and get it rented out or buy a multiplex.

Do not buy real estate if you have bad debts.

I've done my analysis and found a deal that I really like, that has seller financing that balloons in approx 2 years.....cash flow is pretty attractive, but the down payment is around $300k, and I was looking to put d...