Introductory letter from tenant to new property owners?

Our 50-unit apartments just changed hands; the property manager has asked me to write some "letter of introduction". I should mention that I am a senior who has occupied same 1-bedroom apartment for 37 years, and the present management has actually granted me only a token increase in rent that charged the equivalent rate for a studio apartment ($1925 v.s. $2250/mo.) in recognition for my extended tenancy.

I am unsure how to write said letter, what format/terms should I address, while expressing appreciation for their consideration to date?

I should point out that this is an expensive neighborhood within a high-tech county in CA. I worked and retired here with no problem, but recent developments make the cost of living problematic. I am over 80, live alone on my savings and social security that allows for few luxuries. With these considerations in mind, how do I compose an appropriate message to the apartment management?