Get educated and make an educated guess on where to spend money.

Then don't rehab for zero COC return.But if you can spend $3000 on the lite rehab and increase rent from $1000 to $1050 then you'd gain $50 per month.50 x 12 = $600 more annually because you rehabbed.600 / 3000 = .2 or a 20% cash on cash return! 

They spend a ton of money on advertising their product and apparently have none left over to spend on product development.

(Then you have zero vacancy, your business controls its rent increases, etc.)Rent out the garage to another small company. 

Also you would not reduce the price because of the interest payment. that is not how it works.3. yes the note could be sold, but at what type of discount and what if the borrower stopped paying.while there are a lot of posts on seller financing, some estimiate less than 1% of all transaction have seller financing and the ones that do are first position only with an average of 30% down payment - most of these are to people who do not have verifiable income.Thinking you will get conventional financing then seller financing will be uphill battle as the conventional lender most likely will not approve a 2nd mortgage for purchase.not trying to dissuade you, just wanted to provide some key insights so you do not spend 1000 hours chasing something that is impossible to find.

Learn by doing, not by paying.You can do all the right things after spending $40,000 on mentoring and not end up with any real estate.If you invest in a project.....very low chances you end up with nothing.   

Seller is an investor who sells dozens of properties each year (some of them via fsbo) but ultimately give in and choose to let you list b/c they’re having trouble offloading this particular property OR want to spend their time on something else.

For the 4 plex you are spending an extra 80k in renovations (I question your 110k renovation number to get to 4 units - this could be low but I don't know the square footage or layout).

Have a bit more control of my time. 

Educate yourself on the differences between checkbook control and custodial control.