so work ouit what columns you need
work out he type of thiose columns
find the size of those columns,
add some fudge factor (for overhead, indexes and so on) I'd guess at around 15..35 %
..and multiply by 100 million
the imponderables are
do you want to store images inside the db, or merely pointers (URLS) to where the image is stored, that save a fair amount of space in the db, but is zero sum gain, becuase you still have to store the image somewhere
any db shoul; dbe able to handle that sort of requirement whether thats going to be file server db's like Access, Filemaker, SQLlite to server systems such a MySQLm MS SQL Server, DB2 and so on.
a lot depends on who you see usuing the DB, the more (concurrent) users then the more you should be lookignm to server DB's. if you are thinking of using a web DB then consider using a server, the choice of which depends on your internest serive provider as to what they offer, what cost and what experience you have.
the cost of an application is not just the running cost, or the development cost its also the maintenance cost. and that often depend on what sor to fhardware and swhat sort of software you use. some are free, some are free depending on what use you make of it, some cost from day one. ferinstance an Oraacle licence couldcost big time each and every year.
the development cost depends on what tools you use, how experienced your developers are (ie how quickly can they convert the outlien into a specification, then application. It also depends on how much you want to do with the applications over the life of it.
I'd rather be riding on the Tiger 800 or the Norton