Great tools that get updated regularly.I am on the lending side of things and would be happy to hop on a call with you anytime to discuss financial strategies and help answer any questions you may have about nearly any loan product available to help you on your journey, even if they are not products my capital partners offer.We are all here to help you learn and grow.

https://www.biggerpockets.com/...12 Frequently Asked Questions (And Answers) About DSCR Loanshttps://www.biggerpockets.com/...

You're increasing the need for hot and cold air dramatically and it's doubtful the existing system will be adequate.But, in answer to your original question - yes you will need a permit.

When they answer, you say Hey ___, I'm ___.

Happy to connect and answer any questions you may have. 

There truly is no right or wrong answer.

I know this may not seem possible, and probably not the answer you were looking for, but it would be worth partnering with another active investor, bringing in a passive investor(s), or even waiting until you have enough capital to deploy into the right deal. 

To answer the question about your DTI, if you are going to be utilizing a DSCR loan for any new investment properties, your income/DTI is not going to be factored in. 

.: sounds like the best answer is in the mirror. 

It's a question that is impossible to answer without some market research.