Help with new floor (vinyl planks)

[thechallenders]

My husband and I are getting ready to lay down new flooring in our manufactured home. We purchased it used and have been remodeling it. We're finally done with everything and ready to redo the floors.. We're now pulling up the very ugly carpet in the livingroom and dining room, and will be laying vinyl planks in both those rooms plus the kitchen and breakfast nook, which are all open rooms, so a continuous floor plan. The kitchen and breakfast nook have vinyl flooring right now.
The vinyl planks we're using are from Lowes, are 4" wide by 36" long and are the peel and stick kind. We also purchased Henry's floor primer to make sure we get a good seal..
Here's our question. After pulling up the carpet in the dining room, we've discovered that there's a slight gap (about 1/8") where the house meets in the center.. The sub flooring is OSB board.. The two sides do appear to be pretty level.. We still have carpet to pull up in the livingroom, but when we pulled it up to look at it, it does appear level...
But we aren't sure what to do about this slight gap between the two sections.. do we need to fill it in with something before laying the planks or do we just start laying the planks along that seam, covering the gap, and work outward from there? If we need to fill it in, how do we do that and what kind of product do we need to buy? Also, has anyone else used this type of peel and stick vinyl planks over OSB subflooring? As long as we use the Henry's floor primer, is there anything else we need to do before laying the planks?
Thanks for any help you can give us..
We're older DIY'ers (upper 50's and 60's), and selected this type of flooring after a lot of research... it sounds like this will be the easiest floor for us to do ourselfs...

[1987Commodore]

Welcome!
You will have to fill the gap with something, or you will eventually have a dip there showing through the planking. Place a straight edge across the marriage line and slide it along the length of the room to see if there is any difference in height from side to side you will have to make up. There are liquid floor leveling compounds you can purchase. You will want to feather out the edges a couple of feet on each side to minimize the effects of any height difference. If the surface of the osb is not perfectly smooth, it will also eventually show through the planking. You could probably use the leveling compound to make sure you have a perfectly smooth surface all over.
There are lots of people on the forum who have more experience than I, and someone will be along shortly with more advice.

[hhb]

When we had vinyl laid in our place, they nailed 1/4" "meranti" or mahogany plywood down first over the OSB and stuff to give a smooth level surface. Otherwise the OSB wood chips would eventually telegraph through the vinyl. They also put floor leveller between the seams of the plywood.

That would be why most people opt for a floating laminate floor over anything; all you need underneath is a thin layer of foam.

[DCDiva]

I like my vinyl planks BUT they show every little bump.dip.crack so prep before hand and check under every piece,and it scratches very easy--if I had the extra money I would have put down hardwood floors but it was a basement,my upstairs has hardwood floors and they are the best. If you want me to I can show you after a year of wear,even with felt pads under everything. and the bumps.dips