The guy drains the line to relieve the backup but we had to use one of our garbage cans to catch the backed up sewage in the above ground pipes.

A multifamily is a good idea-a duplex might be good as the tenants still do the yard work and you don't have to deal with garbage, yard work, etc.I agree with Jaron about planning and not jumping in. 

I heard from a local they use garbage and sand to build up the lot (yikes!).

There's now a garbage can cover leaning against the house over them.

By me in WI in Kenosha it used to be $50k for a 2 unit now its $120k for a garbage one needing 40k in repairs or $170k+ for a good one that rents $1600 with tenants that get evicted and dont pay often LOL We have some tertiary markets like Elgin where you can get decent tenants and $5000 gross out of a $450k 4 unit it still works but is getting harder forsure. 

Who pays for garbage?

I used a 5% loan with 20% down, $2900 in rents, 10% management fee, $150 a month for water,  landscaping and the garbage bill.

Any calculator/formula is subject to GIGO....garbage in, garbage out.  

Pour the grease into that and once the grease has set and the can is full (ie don't use it once time, keep adding to it), put the can in the garbage. 

I also love that you take the time to sell and donate many of the items instead of just throwing everything in the garbage.