It is simple... Add the costs of the models, crew ( you will need some unless you plan to shoot some shitty gonzo), location, some post work and some paperwork + an overhead... And there you have it....your cost. Then add some profit for you to live on and you have a budget.
Lets say you are clever, have some experience in doing all of the above, are good in planning and scheduling... So with 2 models ( female, since I am partial to lesbian) you can shoot pretty good content for as little as $1,000 per day. Planned well that will give you up to 4 h of useable material.
Then you have to decide if you sell it 100x over for 10 dollars a piece ( non exlusive)
Or
Make a deal with somebody like me ( and they are others) who will buy it exclusively if it is any good.
Failing that shoot more corn...
