Systematic Investment Plan (SIP) is a process to crub the volatility of the market. It helps to invest in discipline manner. It allows you to invest fixed amount on a fixed date in mutual fund scheme(s).
Generally, SIPs consider better option for investment because of its feature "Rupee Cost Averaging". It will help you to generate good corpus with time.
You can start SIP investment with a nominal value of INR 100/- (in selected scheme). Although, it is always advisable to invest that much amount required to fullfil your desired goal. You can invest as much you want. There is no maximum limit for SIP.
Any one can invest in mutual funds through SIP above the age of 18 years. Those below 18 years can invest via their legal guardians.