This, exactly. Compound interest. Daily capitalization is crazy.
Assuming you get 3.65% per year (0.01% per day), daily capitalization will turn this into 37%. That's why banks which do monthly capitalization are so much better than banks that give apparently higher interests with yearly capitalization.
I would keep interests as low as possible, if there are any at all. Interest means the player gets money for doing nothing.
Reward-for-nothing kills most games, though in a RTS it may be acceptable as long as it doesn't weight in noticeably. But I would rather have a very small constant income instead. Large enough so a player without units can buy 1-2 harvester units, and small enough so it won't be really useful to everybody else.