Young Money

I joined a family plan with a friend I hardly ever see, and it saves me $500 a year

My friend Mike and I see each other about twice a year, but we're bonded for life by our cell phone bill. Thanks to a recent T-Mobile promotion, we joined up on a family plan under Mike's name that lowers our bills from $135 every month to $90.

Mike pays the bill in full every month, and I Venmo him my share. It could work great and save me $500 a year. It could also be a disaster.

In the CNBC Make It and Bustle series, "Young Money," we explore how the issues surrounding money and friends are not to be taken lightly. We even created a Roommate Prenup to protect you when you decide to share space with a buddy. Why? Because people tend to go into those kinds of situations thinking everyone else has their best intentions at heart, and they are often proved wrong.

With that in mind, I surprised myself by agreeing to this deal with Mike. It seems like the exact scenario that may come back to haunt me in eight months. What if Mike forgets to pay the bill and I'm left stranded without my phone.

Mike was also a little nervous: What if I stiffed him for the bill? (I would never!)

With the Roommate Prenup in mind, I wrote out a quick email to Mike that said, "I promise to always Venmo you cell phone money ASAP as long as you promise to always pay the bill on time."

He wrote back, "You've got my word."

Does this really mean anything in a legal sense? Probably not. So, just in case, I also called T-Mobile, and a rep assured me that it is always possible to pay my share of the bill on my own, since the costs are separated under two different phone lines.

Doing the research to make sure I can save money and still look out for No. 1 made me feel comfortable entering this agreement with a friend. It also saved Mike and me from potentially straining our friendship down the road over a cell phone bill.

From splitting the check to DIY adventures, "Young Money" helps you navigate tricky financial situations.

Check out more in the series:

Like this story? Like CNBC Make It on Facebook!