Most models price custom content by the minute. $5 to $10 per minute is pretty normal, but there's A LOT of variation. Models just starting out generally set their prices on the low end. However if you are a couple, that would raise the price.
If you're going to be focusing on custom content, then you probably want to set your subscription price low, or even free. If you decide to do regular (e.g., daily) posting, then $8 to $12 per month would be normal (lower if you're going to post a lot of PPV content, and higher if not).
If you are starting out my two cents is start with a very robust free page and sell content via PPV. PPV prices for most non-celebrity creators run from $5-20.
In order to make money you need a fanbase to sell to. Make sure to start that process first via social media and other platforms.
It's going to be up to you how much you want to charge, always price things at a price you're going to be happy with so if after you make a sale and you feel not that great about it that means up your price.