Most of the time, index fund investors will invest at regular intervals, such as weekly or monthly. Occasionally though, we may be lucky enough to come across some extra money. This may be from the sale of a house, or maybe you are thinking about starting to invest.

Naturally, this leads to one of the most common investing questions. Should I invest it all at once (lump sum), or spread the contributions out over a longer period of time (dollar cost average)?