Hi Helen and welcome to the forum
An IVA should take no longer than 6 - 8 weeks to prepare, providing there are no complications with your case - such as needing to effect a re-mortgage to extract equity. Your first payment into the IVA is usually due as soon as the IVA is accepted, and some IP's will ask you for the first payment to be made prior to the IVA to show good faith on your part. This should be refundable in the event that your IVA is not accepted.
All other points have been ably dealt with by Ivor!
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk