Before I buy anything, what does showing up at a county auction cost?

Take the three costs in order.

Data first. Your county's public notice list is usually free, and it's the same data the paid sites resell. Paid aggregators typically run somewhere around $50 to $150 a month, and some charge per lead or per skip trace on top. They buy you convenience and speed, not secret inventory. The $59 site with photos of everything is overselling itself, because nobody has interior photos of a house that hasn't been repossessed yet.

Title work second. Before you bid you want to know what liens sit ahead of the one being foreclosed. A search runs roughly $75 to $250 per property depending on who does it and where, and an attorney's opinion costs more. That's the number that stings, because you'll pay for searches on plenty of properties that get postponed or bid past you.

The deposit last. Terms are set by state and often by county. Some sales want the full price in certified funds the same day, some take a deposit at the fall of the hammer with the balance in 24 hours or a few weeks. Your friend isn't making it up, that pattern is real in a lot of trustee-sale states. Get the terms in writing from the trustee or sheriff running your specific sale.

The part people miss when budgeting: divide your research spend by the deals you actually win. If you search ten properties to buy one, that one deal carries all ten searches. Underwrite for that, not for the single search on the house you got.