Money talks, bull**** walks.
I expect this and if I want something I expect to pay for it right then and there. Until a payment is made, I don't expect anything from a seller.
It's unfortunate but "lowered expectations" is necessary in this day and age.
I won't do "handshake" deals as a seller either, or tell someone "I'll hold it for you". I tell them honestly whether there have been any other inquiries or not and that if they want it, come get it with cash in hand (or acceptable method of payment). If someone offers a partial payment I tell them that's up to them but I won't hold something based on that - if someone else shows up the next day with full payment I'm taking that and I'll notify and refund them immediately 100%. I think I'm not doing anything wrong by that and I've only had one person get pissy with me about it (sold some bike parts - they left in a huff because I wouldn't wait until he "got paid next"
and I got full price later anyway from a different buyer) - it's full disclosure. If someone doesn't like the terms they're welcome to pass and move on. I'm never that desperate to sell stuff that I'll risk reputation or conflict.
That's for stuff - for professional services I'm very strict - an hour to hour-and-a-half free consultation and that's it. After that I write a proposal and wait for a reply. I need an agreement in place. It's actually illegal to render services in some jurisdictions (like CA) without as contract or similar instrument in place. And it's just good business - no headaches and it limits the tire-kickers' damage - by setting the "put up or shut up" point early in it avoids BS-ers from wasting my time.