Also, if the home purchased (or refinanced) is your primary residence, some guidelines now state that 100% of rents received can be income used to qualify.

Here are some guidelines for you to follow, and protect yourself;1.  

Fannie Mae and Freddie Mac the two quazi government entities that control the conventional housing market have in their guidelines that a 3-4 unit property has a maximum loan to value of 75%.https://www.fanniemae.com/content/eligibility_information/eligibility-matrix.pdfFHA will allow for up to 96.5% loan to value on a 1-4 unit property. 

As a general guideline it’s not just the NOI for valuing a property.

With the inherent hassles dealing with the bureaucracy and ever changing guidelines, not to mention the hassle with dealing with low quality and low income tenants and areas, low rent rates, I can't imagine why anyone would even dream of dealing with Section 8! 

Would you gamble?

It could be required by statute, by investor guideline, by declaration, or by discretion.

Where can I find a general guide line for new construction budging? 

Do you think that's too much of a gamble?

For example the mortgage industry will typically view three houses on one lot as a "3 unit" property since the word "triplex" isn't to be found in the FNMA guidelines.