ok let me tell you from my experience. I have started a porn tube 7 months ago. My niche was amateur and leaked sex. I worked hard. Uploaded several videos per day. most videos are very shorts. some are in seconds too as thats what belong to amateure and leak sex category. as per today i have 713 such short videos uploaded. And two days ago i was able to get my site listed in world largest porn directory, theporndude.com
right now this is my site's stats,
Unique visitors per day = 3500 - 4500
Pageviews per day = 45000 - 47000
Income method = popads.net
Monthly income = 300$ - 350$
here is the cost i paid,
for .com domain = 7$ (one time)
monthly hosting fee = 5$
for the retrotube porn tube theme = 24$ (one time)
and by the way my site is hosted completely using wordpress cms. now i work only like 10 mins per day in this project. I know my income is low. but if you are in a country like india, its a pretty good income
anyway i hope i answered your question.
thanks