If our 29 year old son is in his second year of law school, we pay tuition and all expenses, and he made less than $1,000 in 2024, can we claim any expenses?

You can only claim the tuition credit, if he is your dependent. 

The primary requirement for him to qualify as  your dependent is that he have less than $5050 of income for the year. 

There are two types of dependents, "Qualifying Children"(QC) and Other ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit and student status test, a relationship test and a residence test.  He cannot be your QC  dependent because he is over age 23 (even as a full time student).

A person can still be a Qualifying relative dependent, if not a Qualifying Child, if he meets the 6 tests for claiming a dependent:

1. Closely Related OR live with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $4700 (2023) ($5050 for 2024).
3. The taxpayer must have provided more than 1/2 his support

In either case:

4. He must be a US citizen or resident of the US, Canada or Mexico
5. He must not file a joint return with his spouse or be claiming a dependent of his own
6. He must not be the qualifying child of another taxpayer