How long should I wait to hear back after an interview? What are my chances to get hired? Please help! (visa, job)

[lockingcat]

I interviewed with a company last Friday afternoon (August 17) and I was one of the top 3 candidates. I interviewed with HR director and department director (the person that I am gonna work for, so I assume he is the decision maker) and I think the interview went well.

I used to work at the same department for the internship after graduated, so before the interview, HR director talked to my old manager and tried to find out things about me. And I believe the manager liked me a lot and told the HR director good things about me (because HR director mentioned that in the interview).

side note: HR director told me that my old manager wanted him to tell me that if the position I was interviewing for didn't work out, she (old manager) might have something for me.

After the interview, I asked them what the hiring process is like, and they told me I will hear from them early next week (which is this week). I sent a thank you letter to both of them via snail mail right after I got out of interview, and the letter should arrive in their office on Monday.
It's Tuesday now and I haven't heard back from them yet.

I know I shouldn't assume anything before I really get the job offer, but it's Tuesday now, and I just keep wondering, what are my chances to get hired? And how long should I wait to hear back from them before giving up hopes?

Thanks for your opinion!

P.S. I'm a foreigner and need a work visa and the company knows it. So I'm wondering if this fact will slow them down to make an offer?

[MrRational]

Originally Posted by lockingcat

...and I was one of the top 3 candidates.

P.S. I'm a foreigner and need a work visa and the company knows it.
So I'm wondering if this fact will slow them down to make an offer?

You can stop wondering now.