Ignore seller finance for a second...Can you buy a house, put 20% down...yes.

Investment Info:Small multi-family (2-4 units) buy & hold investment.

Maybe I’ll buy outside sheds for each unit and rent to them.

Based on your numbers, and assuming you have a credit score high enough and have never filed for BK, you shouldn't have an issue getting approved for an HML to buy/rehab the property that I would estimate at about $370k-$375k (which includes 100% of the rehab costs).

You said you're trying to buy the house from someone who is in foreclosure (not yet foreclosed on).  

Here's a detailed guide on how to screen applicants: Application Screening Guide 

After selling one and using a 1031 exchange to buy a fourplex in Chicago, he reduced his interest burden by 20% while boosting his net incomes by $1,500 per month.

I have seen these circumstances; people die, go out and buy a car, lose their job, etc… Just my own two cents, I’m not an attorney, just play one on TV

Buy in an area you want to live and renting to the people you want to rent to.

I have no prior investment experience but after living in Paraguay, and reading some books about real estate investments, I think I'm ready to buy my first property.