“A person who always pays their debts late” VS “Someone who always pays their debts on time”

Question

I was wondering if there is any word / idiom / expression to define someone who borrows money from relatives and friends and pays them always late.

I know the words:

• Deadbeat
• Welcher

But they tend to indicate someone does not want to pay back at all, while I need an adjective etc. which is used to imply that they pay back, but just (a bit late =/= on time.)

Also, I am looking for the antonymous word / expression which is used to define someone who always pays his debts on time.

Example:

• I won’t even lend Sam a penny! He’s a / an..........
  However, I’ll give my whole life to his sister. She’s a truly reliable person; although she’s jobless now, but if she borrows you can rest assured that no matter how, she’ll pay you back. Everybody knows that she’s a/an............

Answer 1

There are a couple of casual phrases:

She's a class act.

She's a brick.

This one suggests that she is completely dependable.

In more formal English, I think you have to say

She's completely dependable.

Her integrity is unquestionable.

There doesn't seem to be a convenient noun. I mentioned "Mensch" in a comment. But this slang is not common outside of the Jewish community (it is borrowed from Yiddish)

Answer 2

For the extremely scrupulous person I like the description "You could take their handshake to the bank and it'd draw interest".