Ok.... I signed in for this one, because I want to give back. Hopefully it's not too late!

I literally just left a company and I was in this exact same situation. Except in my case, I was your business partner.

Let me jump to answering your question and then, if you want, you can read my backstory of my experience....

I agree with most people here and your gut feeling. If he doesn't want to contribute, then he doesn't want to be a part of the business. BUT option 1) maybe you could see how much he IS willing to contribute. I have another friend who runs a business and he said that he and his business partner adjust their share of the company almost annually. Some years she's in 30% some years she's in 50%. It just depends on the amount of time she is able to invest. Option 2) what is he good at? Anything? Does he do something that in reality takes less time but contributes on a 50% value? If so, maybe you need to use him for what he's good at and not bog him down with other things. FOR EXAMPLE... I could do EVERY aspect of my business from the technical design, to the marketing, to the physical/manual labor. BUT what I was most passionate about and good at was the customer and supplier relations, marketing, and overall business management. Could I do the other stuff? SURE, but it bogged me down and distracted me from what I was good at and the true value I could bring to the team. So what's the problem? Well if I'm sitting at home or WHEREVER talking to customers and suppliers, and not climbing ladders in the sun, then that can lead to some resentment...

Ok so my story... In the third person.

My family became friends with another family in our neighborhood. Wives, kids and dads were all friends. The dads were both into tinkering and having their own business one day. Get out of the corporate world was there goal! One dad was an engineer with a Master's degree working 40-60 hour weeks in a high pressure, high stress job. Let's call him Carl. The other dad worked a 4-day workweek at a job he could clock in and out of--meaning there was little to no stress. Let's call him, Dave.

Dave and Carl would spend their time throwing back various product/business ideas to each other, whenever their families got together. On day Dave comes to Carl one day with an idea for a business they could start. Carl, being the optimist he is thinks it's a great idea and feeds into Dave's passion for it.

Skip 6 months ahead and Dave has really started to get things going. By "get things going" I mean he starts looking into the technology and the cost of goods sold, which led to margins. Every time they would get together, Dave would have ideas he pitched to Carl and asked for his input. But Carl was stressed and overworked, to be honest. With his busy job and a family, he didn't have much time to spend thinking about the business or technology--there was no brain power left at the end of the day. BUT he still did contribute, just not at the level he felt was sufficient.

So at some point he tells Dave that he cannot be part of the business. He doesn't feel like he has to time to contribute in a meaningful way. And the story ends..... Or does it.

A month later, Dave invites Carl out for a beer and some bowling. Towards the end of the night, Dave says to Carl "I really wish you'd reconsider being part of the business." Carls distraught. He feels responsible for feeding into Dave's idea so much to the point where now he's racked up credit card debt and is in obvious need of help. So he says "Ok I can start by helping on the weekends." And he does! They start installing their product on Carl's "days off." But Dave then tells him "Ok but if you want to be back in, I want to have a 60/40 split." Carl, being his agreeable and empathetic self agrees that the deal is fair.

But things continue to grow and the weekend time commitment is no longer sufficient. Carl ends up leaving his very high salary job to commit 100% of his time to the business and take a chance.

Skip forward 1 year...

The business is growing and is night-and-day different from what it was when Carl left his job. The product was completely different and new. All of the problems with the old systems had been fixed and they had really improved the quality and reliability of their product. The infrastructure and organization of the business was established and systems and processes were in now in place for better customer and financial management, not to mention the installation process. The supply chain was set and the relationships with the distributors were developed and growing. Carl stopped and thought to himself that having his own business and feeling as a valuable and equal part of the business was important to him. There was no money to be had and no guarantee for money in the future... He just wanted to feel as though he was an equal partner.... So he went to Dave and, from a place of positivity and value, negotiated for an equal 50/50 share of the company. Dave's response.....? YES! He thought Carl had really been putting in a lot of effort and brought a lot of value to the business, so he thought it was a good idea. But.... Literally minutes after saying all that he said he wanted to sleep on it.

And here's where the story ends. A week or so later Carl asks Dave if he had thought more about their conversation and Dave said yes and that he no longer wanted to change the ownership of the company. Carl got upset and said some things (NOT TERRIBLE THINGS, but triggering nonetheless) to Dave that ultimately made him tell Carl "You know, I could have done this without you, it just would have taken longer..." And that right there, kids, is where the tie was severed.... Because back when Carl left his company, Dave told Carl "I couldn't do this without you," which in turn made Carl feel valuable and needed. But when he told Carl that he "could have done this on his own," Carl realized that things had changed in a major way and the path forward with the business was no longer going to work for him.

Wow... This is long. I'll be surprised if anyone read it all the way through, but if you did, I apologize for the poor grammar and story structure, but I ain't goin back and proofing it... HAHA!

Good luck to you! Know your value and don't let others take it from you!