My primary residence has a unique feature in that it has come with a 20x40ft double-wide manufactured home in the backyard.Previous owner was using it as a shop but it has wood panel walls and beat to hell 50 year old carpet. 

My only recommendation to you right now is to spend the money upfront to be protected and enter this deal with eyes wide open.

I love real estate but seems like is not for me, I was trying to put a brand new doublewide in it, I got approved for the loan but really don't have a clue about asking price for the property, I asked my realtor and she said 'well just add lot price plus house plus some cash for you' there is no comparables since all the mobile homes I see around are used and old, the price for the cheapest double wide will be close to 55k I was wondering how much should I ask for it , may be not worth maybe I can build a small house for that money??

I have a feeling that I can get $1150 to $1200, but with the wide range from the PMs I am not for sure.

Would an 8" wide handle the irregularities better than a 6" plank?

Also, consider that Conex boxes are limited to things under 8 feet tall and less than 8 feet wide. 

You don't want a wide receiver blocking for a running back. 

He just renovated a single wide, put washer and dryer room right in the middle with separate door with locks and is renting the place out like a duplex!!  

Flippers have to have wide margins and then resale.

No idea why CFPB carved out that exception to what is widely viewed as a "good" consumer protection rule.