Ok, there are 4 types of common forks.

1" Threaded (several different threads)
1" Threadless
1 1/8" Threaded
1 1/8" Threadless (most of the MTBs and hybrids, even road bikes in the last 5 to 10 years).
(plus some more custom tapered forks, especially with carbon fiber bikes).

Oh, are you buying new or used? As HillRider mentioned, it is ambitious to buy a new bike and do major changes immediately. A used bike? There are a lot of good used non-suspension bikes available, but you have less money invested in the bike, and have to take what comes along.

Also at least or local co-op has a whole wall of battered MTB forks. Something would surely fit. Do you have a local bike co-op or bicycle recycler?