What expenses are there on manu homes as opposed to more traditional stick houses?

Good for short term bridge to traditional financing. 

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. 

Traditional wisdom is 1 year minimum.

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. 

So I believe you will have a hard time unloading them in traditional note investing circles.Maybe market to people with SDIRAs.

But if I'm using private money to fund it as a "cash deal" then I wouldn't pay as much as I would if I were going to closing with traditional mortgage funds, right?

Your problem is that you may have trouble securing traditional financing because of your debt.