(I will agree with rudy that a datetime column would be helpful, considering the future, but for the purposes of this specific query, it's moot, as the order of events doesnt matter to a flat total. If you need to make sure the person never went into negative balance, for example, datetimes are a must.)
That said. This is a... confusing table structure.
What is the purpose of 'type'? Surely it's redundant; if FROM = you, money went out from you, if TO = you, money went in to you.
What does the type field hold if user 11 gives money to user 22?
Two ways to change it:
Type = In/Out, ID field.
(ID = party involved, Type is whether to add or subtract from balance).
Cons to this table: Just because User 11 sent out 10 dollars, and User22 received 10 dollars, does not mean you can say user 11 paid user 22.
No type field, 2 ID fields (From/To)
(ID = 0 = 'unspecified user')
Cons to this table: Possibly harder to construct a balance query due to having to do conditional statements.