Jimmy is pretty spot on
Having been a landlord myself and managed my own property I want someone with some stability ( as Jimmy said)
Secondly if I received a letter from a prospective tenant, well I’d just chuck it in the bin. Sorry to be so harsh
As a landlord I was more interested in meeting in person a prospective tenant. I never refused to meet a prospective tenant.
Thirdly make sure you have solid references. Employer, minister of religion, doctor in fact anyone (except afriend) who has some standing and can vouch for you. I always called the referees so written references also go in the bin.
Real estate agents are good references for me. If I can call an agent and they tell me you pay rent on time and never damaged the property and were not evicted, you go to the top of my list
Make sure you can show a SOLID ability to pay rent.That means a steady source of income that you can show has been in process for some time.
Over some 30 years I had a lot of tenants. Never had a bad tenant ( ie trashed premises or unpaid rent).
I often chose tenants that other landlords would not take with great success ( for me and the tenant)
I believe that getting past the real estate agent is SHaaa biggest challenge.
Good luck