What devices do you need if you want to shot a decent quality short-metrage film?

I mean, what's the minimum quality required for a camera, if you want
to make this movie look really professionnal work.

And what about sound recording devices and lights?

Please can you also give me names of brands, and the prices.

And also, can I buy them "used", on at auction or something?

I will hopefully soon shot my first movie, which will be actually a
sort of "demo", and I want to send it to some production studio firms
in Europe and in the USA..

I have written already 25 screenplays, but I still keep them secret (I
haven't copyrighted them yet).

Thanks
PS ; And what computer programs should I use with those machines?