Need help to figure out what a good " rakeback " on 5 pcent no cap

Hi guys , there is a good spot popping wich is 5 pcent no cap basically , starting at 120bb cap to 20bb cap at the biggest table (lol) ; so its basically almost unbeatable as it is. Now they looking for " regulars " players to start table and entertain etc but keep the rake in place . They are willing to pay an hourly rate of " rake back" but im not sure about what i need to ask for.

So for exemple lets say its a 5/10 USD 5pcent no cap , how much big blind by hour should i be paid for the game to be properly beatable. So far games are very soft. I used to be paid 100 usd /hour for opening and keeping alive a 10/20 USD with a 5 pcent rake 100USD cap and a similar soft field , so in this case it must be a lot more.

Thanks in advance