I'm brand new to Filemaker server. Am looking at a copy of FMP Server 7. But, most development work for DB's to be hosted was done on FMP 6. Will this be a problem?

I know FMP Server 7 was a BIG upgrade, so I'm not sure if it can handle and work with FMP 6 files. And if the clients with FMP 6 installed can still open the files hosted by FMP 7 server.

make sense? Any help?

No it will not work. FM7 and up have a completely differently file format than FM6.

Thanks - any leads on a 5.5 or 6.0 server?:

Server 5/6 died a long time ago - think forwards...

Even FMS 7 is quite dated (and was very buggy) so the only real answer is to move up to FM 10. There are some starter bundles which include FMS.

The process of upgrading your existing files will be done automatically when the files are first opened in FM10 - although there are many other things that need adjusting manually. The size and scope of the existing solution will be the driving factor behind the number of adjustments you may need to make it all work.

I converted my own 40 files system 2 years ago - it 3 months to plan. Mine is a particularly complex system and had to remain "live" at all times.

No matter which way you look at this you must move forward as the FM5/6 clients you have will ultimately fall foul of operating system upgrades.

I would advise professional help to do the upgrade.