Most common advice is find a customer and then build...This is like most difficult and could turn out to be time consuming...I would twist it to say..Find a prospect, talk to them and then build...With so many people trying to do stuff or saying they want to..A lot of trust on whether someone will really come back with a software is less...And being first timer very few will pay you.... There are exceptional cases where you might find a customer..But then it turns into a service contract than a product development..

Having a a prospect, a channel for repeat feedback on your MVP could be a good start...and mid way through your dev..start looking to convert prospects into beta and then paying customer.. Spending 6 months just to find a customer and not touching product work isnt a great idea for me...