oh honey,
that all sounds very rough. thanks for sharing. i would say that a 5 year old is old enough to understand about things costing money, and where the money comes from. he is only asking out of what he knows-----when you enjoy swimming at the city pool or hiking together, he'll start asking for that. i don't tell my three year old things like, "we won't be able to pay rent this month", i just explain that we get money from mommy and daddy working, so we aren't going to buy that today so mommy and daddy can be home a little more.
i was one of many kids, one income, but saving money was like a game, a challenge, and we all had so much fun doing stuff together. we didn't know until later that we were poor.
i hope that helps you feel a little better, and that things look up for you soon. hugs.