Not quite, but the mistake isn't what you think. When comparing things you must use "than" not "then". Otherwise, both of the sentences are possible.
Both sentences are of course hypothetical, but:
Sentence 1. uses -ing which implies that speaker things that the stealing would have happened over a period of time perhaps there would have been several acts of stealing.
Sentence 2 does not use -ing. This does not, however necessarily mean that the theft would have occurred all in one go although it certainly could happen like that, but that the time over which the theft would have occurred is of no concern to the speaker.
To all intents and purposes there isn't a great deal of difference between the two sentences.
In addition, in that context, -ing tells us that the event (i.e., stealing) has happened before--you' have stolen money from me in the past--whereas, the base form (i.e., steal) tells us that the event hasn't happened.
Here's the rule:
Participles express an actualized event, whereas Infinitives express a potential event.
Actual/True event: stealing (You have stolen money in the past)
1. It is better then having you stealing my money
Potential/Hypothetical event: steal (You have not stolen money from me in the past, but you might steal money from me in the future)
Are these correct? If not, why? What do they mean?
1. The shipping cost for most items is based on the item's size.
2. The shipping costs for most items is based on the item's size. (What's the subject and verb for this sentence? Is 'shipping' singular? Is so, should 'cost' be 'costs'?)
3. It costs $10 for shipping. 4. It cost $10 for shipping.(If this is incorrect, why? #1 is correct?)