>1) Anyone see any issues with asking a potential client for a retainer? If so, how much?

I haven't asked for a retainer directly. Normally we will offer a contract that has discounts for prepaid hours - works very well to get cash up front.

I do not see asking for a retainer as an issue though.

>
>2) Any problem with putting in a kill switch? When they pay, you give them an access key. If they
>don't enter the access key within days, software stops working.

I've done it before, and I put it to use on an application I wrote as a subcontractor for the US GSA. I wrote the app, installed it at the GSA, the clients were thrilled and immediately put it to use. I was supposed to get paid as soon as the GSA signed off on it (they did immediately). No $$.

The GSA asked me to do a couple of modifications. The Contractor said to do them (hourly billing). Still no $$.

Finally when I delivered the modifications I had a 30 day timer on the app (a VFP/SQL app).

No $$ after 30 days - the app came up with a 'Sorry - your evaluation period has expired message".

$$ by cashiers check (we demanded that at that point) that afternoon.