You don't fund your reseller sub-accounts in general terms (some might be confused by the thought of funding each independant sub-account under the reseller account), - however if you are using the API to sell individual names via your website, the "buyer" buys the name at the required price, but if the required price didn't meet the cost of the domain + Enom's charges, you as the reseller would foot the bill.
Hence if you have an account to buy at $8.95 and you resell at $8.95 using the API, you would be charged the difference for every domain you sell - not good business practice! So you can't do it. To sell at a lower price you would need a $6.95 reseller account.