How to split ownership with partner who will be absent for 2 years

A friend and I plan to start up a small business selling room and equipment reservation software to schools and businesses, beginning locally. To start, please know that we are both 18 years old and very new to the process of starting and running businesses. This will be our first business. We have decided upon an LLC to boot. Unfortunately, my friend will be leaving for a religious mission at the end of the summer, and will be unable to talk more than through about a couple emails per week for the span of two years. We have put equal effort and time into the software we have created, and will invest equal shares into starting up the business.

Our problem is in deciding how to split up the company, due to this absence. We considered starting off with a 50/50 split and gradually transferring ownership to myself as time goes on. In this way, should we make any profits, he will receive his fair share for how much work he has contributed in the beginning to creating the software and for being a founding member. We are unsure if this is the right way to go, and we have not worked out the details, such as the minimum ownership that he will end up with, how to deal with adding new partners over the span of those two years, etc.

If you were in this scenario, what would you do?

Thanks for any assistance, it's extremely appreciated.