4-2-4

Here is a link to the full publication NCAA Transfer Guide (4-2-4 details are on page 22). The rules are different depending on your specifics and since it's critical to get it right I always recommend that you contact them directly:

Eligibility Center customer service
8 a.m. to 6 p.m., Eastern time,
Monday through Friday.
U.S. callers (toll free): 877/262-1492

Calling the NCAA is certainly a good plan. In case you'd like to have an advance idea of what they may say, here's the short version. To be eligible to compete, any transfer baseball player must enroll full-time in the fall semester (14.5.1).
A 4-2-4 transfer must (14.5.6)
1) average 12 hours of transferrable credit with 2.0 GPA per term of full-time enrollment.
2) a calendar year must have elapsed since leaving the first 4 year school.
3) The player must have graduated from the two year college.

There are exceptions for a player who is returning to his original 4 year school, for players whose original school didn't offer baseball while he was in attendence, for players leaving a school which discontinued baseball, or for players who haven't participated for two years. The Transfer Guide doesn't mention these relatively rare exceptions; see the D1 Manual, Bylaw 14.5.6.

With respect to eligibility to compete, qualifier status doesn't matter. Qualifier status can impact a player who isn't eligible to compete, and didn't complete one academic year at the 2 year school.

Of course, individual conferences may have additional requirements.

Note its average of 12 hours of TRANSFERRABLE credits for each semester at the JUCO. So if your son only takes 12 hours a semester and the 2nd four year school says one class won't transfer, then your son is not eligible. So take a class or two above and beyond the 24 hours needed.

I'd recomend talking to the JC counsler who has seen your son's transcript. My son was a 4-2-4 who only spent 1 semester at a JC (redshirt sophmore spring season). before transferring to another D1 Graduation rules from one JC to another will vary. Many D1 coaches aren't familiar with the 4-2-4 rules.....you may need to educate some of them.....