So your question, is it worth it....well only you can answer that. Since the NOI includes the lease rate looking at cash flow with 20% down and at WSJ Prime rate (your probably not going to get prime btw) over 15 years your looking at $22,932 in financing cost. This is IF YOU CAN GET IT FINANCED and that is a big IF because its leased car wash....arguably your paying for the right to work the property and earn the income there is no assets to back the loan in a worst case scenario....and banks don't like that.
But removing your financing cost from the $50k NOI leaves you $27,068 NOI assuming all your other cost are in the $50K NOI. That's not a bad return on your $50K down payment BUT is worth the time, energy, and work your about to get with owning car wash????
Only you can answer that.
Personally, I wouldn't do it because its a lease but if your comfortable with the lease, then decide if the return and work load are in line for you, your family and life.