Communicating without conflict - is it possible?

As I've posted here before, we are thinking about moving to a new house and renting our current one. Financially we're fine; I work full-time and make a good salary, and my credit rating is very good. 

The problem is mainly this: moving out of our current home, in order to get it ready for renters, would take an enormous amount of work. DH has used the bottom half of the house for 10 years for his own personal storage of all his collections and has not cleaned it in that time. We had multiple water leaks (that he promised to fix) that finally I took care of this last year, which ruined the carpet and probably damaged the sheetrock, the floors downstairs are completely trashed by cats/spills/water leaks, there is a ton of other work that needs to be done other than this. It would take a dedicated person who worked on all the stuff that needs to be fixed approximately 10 hours a day for at least a month; if I hired a crew it would probably be done in a week or so, but that's super expensive. 

Anyway, yesterday we were talking about whether it's smart to move right now or not. I love our little house, but it is LITTLE, :). I'm fine with not moving and just improving on what we've got here. 

He wants to move, and is adamant that HE could do all the work that needs to be done in a couple weeks. Judging from his track record, I have a big problem with that:

 - he has two storages that I've been paying for for ten years that he told me would be cleaned out in a month 

 - My "office" downstairs was supposed to be cleaned out two years ago, still full of garbage

 - The other room downstairs was supposed to be cleaned out two years ago, still full of his collections. 

 - Instead of working on stuff he promises up and down is going to be done, he goes and volunteers at local comic book shops for trade and comes home with literally carfulls of stuff


So I was understandably a bit skeptical when he said he could get the house renter-ready in 30 days. It wouldn't impact him at all, but I could end up having to pay two mortgages for months. Judging from his track record, this is most likely what would happen.

If I would say any of this to him, he would argue with me for hours to the tune of "I took four boxes to Goodwill last week!" and such. He doesn't  understand or refuses to understand that this is the same thing he's been telling me for years, and yet nothing has changed. 

I hate arguing with him, but how do I get him to see that he's not reliable? That what he's telling me - getting the house ready in 30 days - is completely unrealistic? 

I ended yesterday's discussion civilly (didn't bring up the above at all) with something to the effect of "let's see what happens", which is basically a catch-all phrase that could mean anything. 

I think the bottom line is this: if I want to move, I'll need to arrange everything myself (big surprise), including getting our current house ready for renters. I'm fine with not moving. But how do you communicate to your ADHD DH that he can't be relied upon without causing conflict? My solution is just to deflect and distract, and it seems to work. 

Sorry for the rambling post - lots of stuff going on here, LOL.