The idiom bet the farm is often preceded by words of caution, as in "I wouldn't bet the farm on that new invention if I were you," or "He might offer you the position, but don't bet the farm on it." It literally means to risk virtually everything on a single investment, idea or opportunity. Under certain circumstances, such risk-taking behavior does pay off well, as in the case of investing one's life savings in a small computer company called Microsoft. At other times, however, it means to lose the farm when the seemingly risk-free opportunity goes bust.
Many times a person will use the idiom when an outcome appears to be guaranteed or inevitable. Few investors would willingly bet the farm on a risky or unproven business concept, but some opportunities are simply too potentially lucrative or risk-free to pass up. In exchange for taking a significant financial risk, there may be a very significant financial reward for the risk-taker. A stock broker or other financial analyst may suggest that a potential investor put everything on a very promising stock, or a real estate agent could advise a client to spend a lot on a valuable piece of property.
There is also a negative side to the idiom, however. Some investment opportunities or business proposals are so fraught with uncertainty or heavy risk that people are advised not to bet the farm on them. Investing all or almost all of one's personal wealth into an unproven or speculative venture can have disastrous results, so a person should always seek out professional advice or do their own research before betting the entire farm on anything. Once the farm is lost, it may be lost for good.
Certain gambling and card games provide players the opportunity to "bet the farm" on a promising hand or high-odds payoff. In the poker game Texas Hold 'Em, for instance, a player who is low on betting chips but holds a strong hand can literally go all-in, meaning he or she wagers all of his or her earnings on the outcome of a single round. Professional gamblers rarely go all-in unless the chances of winning are exceptionally high. Winning a big hand is often a matter of balancing risk versus reward, and there are indeed times when it pays to bet the farm on a promising opportunity.