We all had to start somewhere, even you, so don't be so hard on inexperienced buyers. Sometimes you need to explain things to them and have a little patience. I learnt early on to have BIN rather than auction, because of the problems you face. I found that non paying bidders were not just new buyers but from people who had been on eBay for years. There are no problems with Buy it Now items, it appears the sale does not go through until they pay. even without "immediate payment" being selected. However, if you switch to BIN and want to offer combined postage, you need to change your settings in "site preferences" to allow for combined postage, so the buyer will get the "request total" button and can wait for you to send an invoice.