You should double up the marketing.
On the rental units (non-owner occupied), sent TWO pieces of mail each time: one to the landlord and one to the tenant.
To experience the biggest results, you want to mail THREE different pieces each mail-out:
1. To the owner occupant, send traditional “Sell with me” or “Sell & buy Up with me”.
2. To the tenant, send an “Owning is Cheaper than Renting” piece.
3. To the landlord, send a “Sell with me”, “Manage with me”, or “Ready for more rentals?” piece.
Custom design each piece to each market segment and you will dominate your niche.