You do your research which will help better than my rough guideline.
Dividends are not guaranteed. If the fund is regularly giving dividends in the past, it will likely give in the future just that it's not guaranteed.
Yes, I think there is provision for investing whenever you want. I guess you pick one time investment when you're starting, the amount doesn't have to be a big one (check what's the minimum for the fund you pick) and invest further whenever you feel right. General guideline is you don't withdraw more than the average annual growth of the fund, preferably about half or less (If CAGR is 12%, withdraw 6% or less per year). So that you will have both passive income and let the fund grow. If you're taking pain to find right time to invest further, take some more and find the right time to withdraw as well and go for growth fund instead of dividend fund.