I'd say it depends on how much you value this client's goodwill.  If you would prefer to maintain a cordial relationship with the client (can be quite valuable for future references), then I'd finish the 20 hours you said needed to be completed to finish their project as quickly as possible, and offer the completed work in return for payment in full.  If you don't value their goodwill to that extent, then push for some amount of payment, but make it clear that you're asking for payment because you need to cover expenses related to their project (in this case the expenses are a risk-reserve related to possible payment dispute, but don't tell them that), not because you don't trust them.

Just my $.02

==Joseph++

P.S. Clients who don't like to pay is one of the reasons I stopped doing (independent) consulting about 10 years ago, it became too much hassle to argue over payment (even with contracts) every third gig.  Contracting firms may take 20-30% of the payment, but oftentimes it's worth that just to avoid the hassle of negotiating contracts and getting clients to pay their bills on time.

JD Austin wrote:


Bart Garst wrote: 
On Thu, 2005-04-14 at 16:07, JD Austin wrote:
  
I asked this guy for a good faith partial payment of what he owes to
test if he will pay at all:
    

... snipped ...

  
This guy has nerve :)

JD
    

I imagine he'd say the same about you. I think that was pretty
unprofessional of you to post your private business correspondence to a
public group.

Bart
You have a good point Bart, though I did remove all identifying information except that one side is me.
I would in no way disclose who this guy is or anything identifying him to a list like this or to any public forum other than a court of law. 
Unless you knew this guy personally there's no way anyone would know who I am irked about.

I was just curious how others on the list would react to a client saying 
"I'll pay half of what I owe you now if you do another 15 hours of work".

JD


-- 
JD Austin
Twin Geckos Technology Services LLC
email: jd@twingeckos.com
http://www.twingeckos.com
phone/fax: 480.344.2640