My plan has been to start an LLC, and purchase a duplex using traditional financing with 20% down.

A lot of lenders will not allow for this so it certainly needs to go the private route opposed to traditional. 

It is my understanding that you can only have a limited number of properties covered under your umbrella policy and it is based off of your primary redidence?

I believe as long as it’s your primary address you are good.

Traditional wisdom is 1 year minimum.

Then there's ones like my primary home was original to the home in 2000 and still kicking although needs more maintenance now. 

This is the primary reason for my search for financial freedom.

Could I rent it out for exactly one year, and then move back in as my primary residence after the lease expires? 

If the ARV was 85K and 75% LTV was 63K, and I had 58.5K on the HUD and I used delayed financing I could only pull out 58.5K (100% of hud or 75% LTV whichever is LOWER). so that means I end up with $5250 in the deal that I couldnt' refi out, unless I used traditional financing and waited 6 months.

Because I don't have a mortgage and not amazing credit I don't look great for a traditional mortgage through a bank.