Is there a difference in meaning between these two?
Services must be paid.
Services must be paid for.
Yes. The word for shifts the indirect object* of paid somewhere else.
- I must be paid
- I must be paid for
In the first, I receive the money. In the second, someone else receives it in order to cover my cost.
"Services must be paid" means that the services receive the money. It's grammatical, as far as it goes, but it doesn't make a lot of sense.
"Services must be paid for" means that someone (person A) has to pay someone (person B) for the services.
There is a substantial difference between the two.
It may be doubtful whether the direct oject of pay is the recipient of the money or the money itself (which often doesn't need to be mentioned explicitly). But the use of for diverts the money elsewhere.