We have considered renting but we had some work done on the house that was not permitted so it is a big concern for us in renting it out.

non conforming is the usual (grandfathered).. you can ask you permits and they can email them to you usually.. 5 plus units is commercial plus its multifamily 

Otherwise you're looking at 3-4K in labor + permits and possibly crane rental if you're putting it on a roof.

I also have an ADU conversion (with permits) in the works and plan on saving most of my gi bill housing allowance for another unit.

I don't think it's technically permitted to have multiple homes on the agriculturally zoned land here in Orange County, FL, but it's grandfathered in is what my realtor told me.

Having pre-approved plans in your jurisdiction should help the permitting process along, that said buildings are pretty site dependent and if there's any slope restrictions in your area it will make your life quite a bit easier if you are working with someone who has been through that process.

One Airbnb house's permit has been pulled because of a PR violation; 6 hearings are pending to determine whether a violation has occurred; and another 8 investigations have been completed and are awaiting a hearing to be scheduled.  

Building at this time is estimated to cost $180-220 sq ft.This is very much a wilderness area still and unless you are inside city limits, there are few permits and inspections needed when building; which makes it even more important to have a good contractor.As for economy tanking, their are already some food threads on BP discussing it and I posted quite a bit about performance here during the recession.

My question is, if I can’t find a fourplex for a decent price, would it be viable, or even permitted to construct a building under those terms?

Make an offer on a 3 bedroom 1 bath house in a desirable popular neighborhood that has a finished (non-permitted) basement w/ a full bathroom, sink, separate entrance outside & washer/dryer.