"My firm is tight money-wise"
If you do a search on eBay for "Foxpro" you will find a number of copies on sale. And if you look in the "in eBay Stores" portion of the 'finds' you will see VFP 9 at some very reasonable prices.
Yes, VFP will no longer be sold by Microsoft, but we all have applications written in FP and VFP which are still running quite well many, many years after the product has been 'obsoleted' by Micro$oft. M$'s ending product development and support has greatly diminished the industry interest in Visual Foxpro, but it has always been a M$ 'step-child' anyway from the PR perspective.
And yes M$'s ending product development and support has even more greatly diminished people's interest in creating NEW applications with it, but your application is already developed in FP and is looking to be merely migrated into the 21st century. Changing to another development language would most typically require a full redesign to fit the syntax and design approach of the new language.
"I've had a little look at SQL server and VFP beats it hands down for data manipalation."
Well, yes and no.
You have most likely had a look at VB/VBA (the 'typical' SQL Server front end) and VFP. And without a doubt VFP is far superior front end for data manipulation.
But as far as the backends, SQL Server and VFP go, both are quite good, but SQL Server does indeed have some advantages. Creating VFP SQL queries which use syntax which is compatible with the SQL Server backend can be a challenging transition, but it is very do-able.
Good Luck,
JRB-Bldr