Rental increase letter

[David Boroughes]

I have a unit where I have let a fairly good tenant stay on month to month for a few years now. I haven't raised the rent because they tend to take care of all the minor issues which saves me time and money, now it's been about 4 years and I need to raise the rent. Does anyone have what they consider a good respectful letter they use in this situation to let the tenant know the rent will be increasing as of Sept 1? I'm only talking $50/month here, which is still a little below market, but the tenant is long term, so I have 0% vacancy on this unit for many many years, and I have no problem passing along that savings to this good tenant. Just looking for feedback on how some of you others ask/notify of rental increases on units where you have nice quality tenants and are actively involved in the property (I do see the tenant at lease a few times every couple months), so I'm looking for a more personalized approach here, 

Thank you,