Best choice to slab?
 

Please forgive my ineptitude here, while I'm a long-time member cards are actually far out of my realm. I just had a friend ask the best way to sell some modern cards they inherited. None are 1K or more, but some have nice value if you weren't expecting it. (Walter Payton rookie, Bird/Magic/Erving.) Some seem to be $20 max cards on ebay. (1989 Fleer Griffey, 1991 UD Jordan.)

A couple of Q's:
1) Who would be the best TPA to grade the better ones, going in with the intention to immediately sell
2) How much would I expect to pay for this service? Say I had 5-10 cards.
3) Is there a basic rule of thumb as to when to slab? A value cutoff that most use? "If it's a $40 card, it's best to slab, under I sell raw?"

Thanks,
Ken

Preference for those type of cards is PSA. If you submit them on your own, it will cost $20 per card plus return shipping. However, you can submit cheaper through bulk submission groups, like the ones on vintagebreaks.com ($9.50 each for cards with declared/raw value) or blowout.
My rule of thumb is to only grade cards to resell that will likely increase by 3x the grading fee. I normally submit on the $8 bulk special, so I want the retail value to increase by $25. Otherwise I sell raw.

If you post photos of the cards you have, myself and maybe a few others can look and maybe advise you as to whether it’s worth grading them. You can easily pay more in grading fees than the cards are worth or you may have gotten the same price if it won’t grade that high.