It's much more work than it seems!
DH and I have years and years of DIY renovation under our belts. I come from a looooong line of builders and was born with a power drill in my hand and have helped with my family's business and side projects since I could walk. And DH is genuinely the most capable man I've ever known, and is meticulous with planning and detail. We've all the tools anyone could ever need. We completely gutted and modernised a 100 year old house together, and others as well. We've done DIY together since we met; it's basically our hobby.
So we thought buying a rotted little cottage with "fantastic bones" out in the country and making it lovely would be a piece of piss.
IT IS NOT.
We've been here over 2 years now and done absolutely loads to it - structural repair and reinforcement, electrical wiring, plumbing and gas lines, all new floors, all new bathroom, demolished old and built new outbuildings, and more - in that time, but there is still a mountain left to do.
Still pending:
The entire kitchen needs redoing from top to bottom (except appliances) including all work surfaces and cupboards; all - and I mean ALL - the walls need redoing; replacing old and damaged windows throughout; complete new staircase; fixtures and fittings throughout; replacing the entire heating system; doors and frames; and on and on... Most of that, we discovered needed doing along the way and wasn't planned for when we started. And after all that, we can finally get to the final clean up, then painting, furnishing, decorating, and putting the finishing touches on things. And that's only talking about the interior!
Target completion date: out the window.
Target budget: who knows anymore.
And we have loads of experience in this stuff!
You can plan all you like, but you can never anticipate everything that comes up. All the little snags and setbacks chew up and spit out all of your time and money.
With the time it takes to do the actual work, or have someone in when you can't, it drags on forever, especially when you're both working full time. You'll go to fix one problem that needs repairing, and find there several other things you must repair before you can even get to the main problem, and countless additional bits you didn't expect to buy. Or the work/build/repair simply takes longer than you anticipate. There are always snags and surprises that set you back. We are currently waiting for somebody to do some metal work we cannot do ourselves, and that wait is totally blocking work on about 5 other core projects. Plus there's an expense we didn't expect.
Speaking of expense, whatever you think you'll need, multiply that by infinity. Seriously, at least double it, if not more. With all the snags and surprise expenses, we could have demolished this house and had a beautiful new build here in less than half the time, for under what we've put into it SO FAR. And if you're on a budget like we are, you simply cannot afford to complete some projects immediately and must wait to save up, again setting back the time and holding up other work and leaving your HOME unfinished and uncomfortable.
And sometimes you just need a break from full time building any moment you're not at work, or you'll go mad! Sometimes you cannot bear to arrive home from a long day at your job and immediately pick up a drill or saw or level or plumbob a get on with more manual labour.
And the MESS! Dust and plaster and paint and dust and dirt and chips of wood and stone and sawdust and splinters and tools and gloves and boots did I mention the bloody dust?! It's EVERYWHERE, EVERY MOMENT! It's nearly unliveable and definitely unmanageable. It's as much work as the work itself! It seems like every time I wipe or hoover up dust or dirt, more settles before I finish one swipe!
If you're really talking about a gutted shell like what we bought and you really intend to do as much of it yourselves as possible, think very very hard about whether or not you can even afford the time and money to do it. Carefully consider whether you can bear living in an incomplete house, literally living on a build site, for an indeterminate amount of time.
Picture yourself living in a house full of dust and draft, tripping over power tools, unable to use large portions of the house for great lengths of time or simply doing so horribly uncomfortably, with loads of your things stored or covered or packed away and inaccessible, often helpless to make any progress due to one snag or another. It's bloody difficult at times!
Now, I will say that once we are all finished, this house will be 100% our own creation from the dirt to the roof, exactly as we want it. But we may be dead and gone well before then! 
Meantime, though, it's maddening and exhausting and frustrating at times. Some days, the lack of progress and the utter state the house is in is properly depressing. I don't think we'll regret it in the end, whenever that may be, but fucking hell it's hard right now.
Feel free to share this post with your DH, and I'm happy to give any further gory detail or advice if you or he would like. I assure you I can help you talk him out of this!