I have a 1998 Honda CRV. As of a few weeks ago, each time it rains, the rain comes through my hood and into the car where a passenger’s feet would go. Is this an expensive repair? If so is it a necessary one? I have been keeping a plastic bag there to catch the rain. Is that completely stupid/dangerous? I am obviously not very car savvy, and would very much appreciate a response from anyone who might be able to advise.
Any decent shop should be able to fix this problem for little or no money. Your drain tube for your a/c evaporator condensation is most likely clogged up. If you want to fix it yourself, it’s a little plastic elbow or tube poking out of the firewall near the bottom on the passenger side of the car. Sometimes you can poke inside it with a stick or screwdriver to get it unclogged, but you may have to take it to a shop and have them blow it out with compressed air.
Thank you so so much - I feel really dumb. Looking forward to taking the garbage bag out of my car. 
It also could be the drain for the air intake for the heat/AC. In either case as mark noted any decent shop should be able to handle it.
I concur, you may be able to see a wet mess of leaves/pine needles in the bottom of the vent intake in front of windshield where an overflow hole exists near bottom to drain off water that otherwise goes into your vents(your case).