Many applicants lack credit all together, no good or bad, so rigid credit guidelines like 650 minimum score will kill your applicant pool.

Fannie gets more business, in no small part, because her guidelines are more transparent and easier to find than Freddie.

@Derek Krehlinghttps://www.biggerpockets.com/forums/432/topics/89731-guidelines-to-help-determine-property-grade---a-b-c-or-d

Solid deal, but was a good price since it was sight unseen re: the inside and thus a bit of a gamble.

Conventional guidelines are that you can refinance a property, that has a loan associated with it, the day after you close...at After Repair Value (ARV).  

The big box banks and Credit Unions will have stricter guidelines for an investor.  

Here's a link to the raw guideline, if you want to attempt to decipher it.TLDR is that no you do not have to wait six months, but it has to have actually been a cash purchase, or other restrictions may apply. 

You will get the same answer from any lender you ask (unless the loan officer isn't aware of the guideline, in which case you won't find out until you get a denial by underwriting when they catch it!)

As long as you stay within the legal statues and guide lines you will not have to worry.

Or would the buyer builder buy it without the building permit and gamble obtaining it at a later date once they have a variance?