Before launching an online website where you will hold auctions of penny type to be more specific, consider this. The cost consists of:
Software spendings, part and parcel of any virtual business
Server rent which you have to pay monthly or annually for using a domain
Salary costs. Professional technical support, auction administrator (in case you hire one) are a minimum employee set for the starters
Marketing spendings. Well-thought promotion will quicken the result and boost development.