This is a more complex question than it may seem at first. From a simple perspective, you want to analyze what the true expected future rate of return is on the property including all costs such as maintenance, future upgrades, vacancy, taxes and more. Then compare that true rate of return with the other options you have for the money, accounting for differences in risk.
Also Covered:
High Valuations = Lower Expected Future Returns
Impact of taxes and transaction costs
Your desired life trumps the money