Translation:He is afraid of having to pay too much.
Does this "behöva" not translate to "needing"? Is behöva standing in for "måste" because måste has no infinitive?
Behöva can mean need, but also can mean need to or have to. I am just a student here but my impression is that there's a bit of a scale that goes something like: behöva = have to -- måste = be compelled to -- tvingas = be forced to. In the context of this sentence, the weakest form fits best.
Using this sentence could one also say 'han är rädd för att hundar' meaning 'he is afraid of dogs'?
If you leave out the att (that) it’s correct. Your sentence means ”he is afraid for that dogs”. It would be correct if you followed it up with ”biter” (bite) or something, but if he’s just afraid of dogs it’s ”han är rädd för hundar.”
I put down " he is afraid of needing to pay too much" and it was marked as incorrect. Why?
"He is afraid to need to pay too much" is not accepted. Shouldn't it be?
The second "för" in this case is "too" (as in something excesive), so "för mycket" is "too much". What the sentence means is that he is afraid of having to pay too much money (for whichever good or service he was acquiring); not that he is afraid of having to pay for much (meaning for many goods or services).
Thanks! I had missed that. The other error I was asking about was getting dinged for translating it as "afraid to need to pay" rather than "afraid of having to pay." But sometimes the error marking is imprecise.