Correct, you can't. When making an offer on a HUD home you must come up with earnest money of $1000 on a home over $50,000 or earnest money of $500 on a home under $50,000. Your "Earnest Money" is deposited in your Broker's escrow account until the day of closing and these funds are yours to use on any un-reimbursed closing expenses and your $100 down payment. The earnest money is HUD's assurance that your are serious about the purchase and it discourages Purchaser's from walking away from a deal because this money would be lost to HUD in the event the Purchaser "changed their mind".
Additionally, if you wish to have the home inspected (strongly encouraged) the expense of having the utilities turned on and the cost of the inspection is the burden of the Purchaser. Inspections cost between $300-$350. Also, HUD assesses a "re-winterization" fee of $75 between September 15th and March 15th so that after your inspection they can drain the water lines to prevent the pipes from freezing and breaking.
There should be no additional out of pocket expenses (beyond the $1000 earnest money, and only a little when using $500 earnest money) if we structure your offer to reduce your out of pocket expenses.