Don't buy without a full inspection. Barn timbers went in wet and it's very common for them to be filled with powder post beetle holes and tunnels. Wouldn't be surprised if they weren't all boxed heart cut at the mill. That puts the pith in the center of the beams.
My plan was to rough turn green bowls and platters and dry them for a finish turning like I do with the logs I get now.
FYI - I just ordered some more lumber (dried) and almost fell over. Prices have gone *way* up in the last year. I’m paying $5.30/bf for 5/4 hard maple!! He told me white oak was over $6/bf !???!!
I’d grab those slabs and either process as green bowls if grain alignment it good, or rip them down and seal like robo suggested.