Not sure if you have solidified/chosen a lender yet, but BP has a list of reccomended DSCR lenders that I think would be great for you to check out.

Start by learning basic metrics like cash-on-cash return and cap rate, and check out resources that dive into rental market analysis.

Be sure to check out the free tools BP provides to help analyze deals you may have and also market insights.

.- check out the BP bookstore and start with 1 book... then move onto the next.

If you are looking at multi family investing check out lifestyles unlimited they have a great program

Me personally, I’d check the contract and try to meet with both the architect and contractor to find a solution. 

Be sure to check out the free tools BP provides to help analyze deals you may have and also market insights.

Check out Nationwide fully delegated banks first.

I would use the local GIS map and check out the owners, back taxes, if they own other property, etc, Always use a Buyers agent.  

Just make sure to check their credentials and experience, and find someone who can explain things in simple terms.Also, keep an eye out for any red flags, like promises of huge refunds without a thorough review or pressure to pay a percentage of your refund.