These loans can have an interest only period of up to 10 years and the DSC ratio is calculated using the interest payment not the P and I.

Don't start obsessing over a calculator for your first house hack, nothing is going to work in California.

What is the best way to use the Rental Property Calculator when you are planning on putting together a seller financed deal?

Ok I will make a  calculation of the rate of closed deals vs/ offer made and I will keep you posted - honestly there is also another consideration that I need to disclose to be correct: my partner is a realtor and this many times facilitate the transaction with other realtors 

An investor friendly agent can do all sorts of helpful things, like setting you up with a search for properties or connecting you with folks who have recently done deals like the ones you want to do. 6) Consider analyzing a deal or two in your local market, just for practice, with a free use of our Rental Property Calculator (or other calculators).

Are we approaching the calculations correctly?

If land is $1M and the value of his services (in calculating equity) is $500K, and we co-sign a $2M loan secured by my land, how should equity look?

Every lender will have their own method/calculation, but most lenders will assume some amount of a minimum payment and apply that in your DTI calculation. 

As someone who has been working with investors for quite some time now some advice I would give you is to learn the lingo & things to learn1% rule75% ARVHow to calculate ARVHow to run rental compsHere is a fantastic website I use for all of my in state and out of state investors.Use this rating and classification system I have created over time to get an idea of the "Class" for the area - A class B class & so onhttps://www.areavibes.com/Here is my rating & classification for each livability score. 80 and above A+78/79 A76/77 A-74/75 B+72/73 B70/71 B-68/69 C+66/67 C64/65 C-60/63 D59 and below F

An investor friendly agent can do all sorts of helpful things, like setting you up with a search for properties or connecting you with folks who have recently done deals like the ones you want to do. 6) Consider analyzing a deal or two in your local market, just for practice, with a free use of our Rental Property Calculator (or other calculators).