Go to this link and scroll down to Site to Site VPN (L2L) with IOS and Site to Site VPN (L2L) with ASA, you can use the links example depicting your scenario requirements, where one end is dynamic and other static for Ipsec L2L IOS-to-ASA or ASA-to-IOS.
The best solution obiosly is having static IP addressing, make that clear with your client , but these exmaples are very good solution for your problem.
Keep in mind that the DHCP dynamic side will always be the initiator to bring up the tunnel , not the static side.
http://www.cisco.com/en/US/products/ps6120/prod_configuration_examples_list.html
Regards
Jorge Rodriguez