Is there a limit on how much stock you can purchase from a company or is there a cap?

A company is authorized to issue a certain number of shares of stock in when they incorporate. However they will usually only issue a certain percentage of the shares that are authorized.

Whatever the shares that are authorized do most companies put a limit on how many shares one person can purchase?

This is not trying to answer your question but I believe, unless this is an IPO, you aren't buying directly from the company. The stocks bought on the exchange are in someone else's hands already and you can buy as much as are available on the open exchange.

Yes this is an IPO, your answer helped a great deal thanks ballengerb1:)