Duplicate Removal And Intelligent T-SQL

I am looking for some T_SQL code that would help us eliminate
duplicate data entry into our mailing db. Finding and removing the
existing dups is not rocket science, but I am looking for a complete
solution.

We also want to be able to come up with a T-SQL script to be
intelligent enough to know if:

"Bill Jones" is the same as "Billy Jones" or

"Bill Jones" is the same as "William Jones" or

"Bill Jones at 123 My street" is the same as "Bill Jones at 123 My
St."

Purchasing scripts from a company is not out of the question. Its a
matter of script cost versus my hourly rate to create them... Needless
to say, something cheap.

We have only heard of one app that is dynamic enough to handle this,
and the cost was way, way out of our range, 6 figures is almost 2
years salary.

Any ideas would be greatly appreciated.