The return depends on the Mutual Fund you select. Assuming that you wish to know the best returns possible, the answer would be in the equity fund category.
While small and mid cap fund SIPs have done very well over the last 3–4 years and given about 30% returns, there is no guarantee that they will continue to do so. Top performing equity mutual funds have given about 15% return over a ten year period.
Going with direct mutual funds, helps you earn upto 40% more as commissions are eliminated. Commissions may seem small but they compound over time.