You can probably just go ahead and live in that 5th unit, but I believe whenever you go to refinance it with a bank or what not, the 5th unit will make it require a commercial loan and not residential regardless of what the county records show the property to be. 

Although I still think conventional is the better option, I wouldn't put 20% down if I didn't have to, unless you know you'll live in/own the house long enough to recoup that additional $. 

Convince yourself that there's a better than average chance that you will lose, and if you can live with the time, energy and money spent if you do. 

Redeveloping into mixed use live/work/play projects has been the most common proposed solution the past few years in my area. 

I'm living in the Los Angeles area and have my projects here.

ESPECIALLY if you’ve lived in any of them 2 of the last 5 years and can take the tax free gain. 

Lived here 2 years.  

Do you want to have airbnbs all over the country and travel between each of them and living an adventurous life?

Quote from @Travis Timmons: Live in flip. 

For example how many post do we see that Say I live in LA which is expensive and need to look OOS .. and how many post do we see that says I live in Cleveland and I want to invest in LA. ???