I think it is depend what you like to do and what kind of porn you like to produce.
If you plan to make porn with pornstars it will be expensive from the first day.
You could start with Amateurs, hire some good guys, find some nice girls and a very good camera man. Produce a nice punch of videos, make 5 min ? 10 min short promo videos for tube sites to promote your porn.
Then get a good host, get a Nats4, setup your main porn site (the selling site), promote your tube videos to webmasters, make sure you have a working export tool with multi options otherwise webmaster will not promote you videos.
I think you should be good with $10K ? $20K to start, after you need the sales but there is the question who pays for porn?
