Buying into existing business

Thinking of investing into an existing business. If I put , say 50k, into the business & become a co-owner, am I taxed on any money I take back out of the business or can the 50k be offset in any way ? Or, whats the most efficient way to get a return on the investment ?

Impossible to answer without more information. "Business" is a generic term. Are you talking about buying an equity shareholding in a limited company, or joining a partnership, or what?