I think the health of the board requires a free to read and post system.
And I have zero objection to then paying for perks like no ads or other goodies.
One board I looked at had this set up:
You signed up and got registered. After registration, you could post only in one forum until you got approved. You could bypass the approval process by subscribing.
Subscribing then had different levels, like subscribing with ads, without ads, buying sticky threads, etc.
I think having options would be excellent. People could then tailor their use of the site to their own preferences and wallets.
And newcomers would have something to gain by subscribing without being forced out the door.