about how much money would i get if i post a old american dollar?

Answer 1

Somewhere between face value and a lot.
Seriously: You need to include a lot more information for us to give an intelligent answer.
The information you need to include is:
The Series (For example, 1934 D. Don't leave out the letter after the year, if any)
Type of note and color of treasury seal (For example, Federal Reserve Notes have green seals. Silver Certificates usually have blue seals, but some have yellow seals)
Approximate condition (Heavily circulated or uncirculated / like new?)
Also: Does the serial number end in a letter or a star?

Do you see how vague your question is now? Follow these guidelines and you will get a better answer.