Wording is important when you're writing a letter, especially if you're trying to carefully word a request. If you're looking for financial relief or forgiveness, I have new hardship letters and apology letters. If you simply want to thank someone, there are plenty of new thank you letters.
If you'd like to create hand-lettered printables, consider taking a custom lettering class so you can edit your designs in Illustrator. Hand lettering is an excellent way to make a printable truly custom.