Landlord dragging his feet on providing a written 1 yr lease for us to sign?

This is in the State of Michigan. My boyfriend and I moved into an apartment earlier this year in a 3 apartment triplex, and it was a month to month oral lease. Our landlord occupied the largest of the 3 apartments in the same house, and he recently moved back to Indiana, and we moved into his old apartment upon the agreement that we would sign a 1 year lease. We have been excellent tenants and have cause zero issues (no late payments, no property damage, etc). It is going on a month now and we have asked our landlord (who now lives in Indiana 2 hrs away) several times to provide the written lease for us to sign. He keeps saying he'll email it so we can print it out, look it over, sign it, make a copy of it, and send him the original while we keep the copy. Several phone call reminders just get us more excuses ("I'll do it when I go to work today", or "I'll go to my parents house and email it", etc). What has us alarmed is that he mentioned that he was thinking of selling the triplex, and he verbally assured us that he wouldn't screw us over by putting us in the position of not having a lease in case he does sell the triplex, which would allow the new owner to evict us or raise our rent, etc. I have written him a note requesting that he mail us the lease within a week, otherwise we will have to do what is right for us and rent from someone else who will provide the security of a lease. He has been a good landlord up until this point as well, but still it takes all of 5 minutes to print out the lease, and mail it to us (or email it even, which he still hasn't done). I don't think we can legally force him to provide a lease to us, and frankly that is the last thing I'd want to do especially since we really like this apartment and we've even made several repairs & painted the interior. We even mow the lawn which is the landlord's responsibility, but we do it just so he doesn't have to drive 2 hrs one way just to do it. I don't understand why he keeps stalling, please help with any good advice. I don't want to assume he's a bad landlord, but what can we do to get the lease? Also, if I remember correctly, he owns the house jointly with his father. Should I contact his father even though we pay rent to & consider his son our landlord? Can we hold rent until he provides a lease?