Hi Maggie
Thanx for your PM...fingers crossed at this end too!!
I am assuming that this is for a Commercial Tender? Then yes, I would state the payment terms at the begining, usually something in the region of: " Payment due strictly 30 days from Invoive date..." or however you wish to put it.
If it is a large sum of money, it may even be worth putting on the Invoice itself: "If paid within 7 days of the Invoice Date the amount payable is: £00.00 (or give a percentage off i.e 5%) This encourages some companies account depts to pay you very quickly.
However, if as Malc G has mentioned, the Company want you to pay on their terms, this can be anything up to 90 days after Invoice date!! So mentioning the payment terms at the begining will sort all the above out. Usually this apply's to the bigger corporation firms, So Management agencies etc that you have been talking about usually pay a month in arrears.
You should always have everything down in writing, even if it is just a "casual arrangement" as this will solve any payment difficulties.....
And to answer your other question, No, it is not the norm to be paid in advance for commercial work.
All the best
Regards
Tim