If you have $300-$400 every month then I think half of that money can be used to buy bitcoin and the rest can be used for daily needs with family. Everyone has responsibilities and maybe in living life not only thinking about investment alone because on the other hand we also have to think about the needs of life as a support for our journey in this world. There is no such thing as too late in investing, in fact the problem is when you haven't started because you are worried that you will always say it's too late.
Invest the amount you can afford and do it consistently at all times based on the purchase period you apply. Bitcoin will give you financial freedom if you understand the pattern and if you don't want to look more difficult then buy and hold the bitcoin you have for the long term so you will wait for the moment of increase at the next ATH.
Actually having $300 to $400 every months still not enough for some one have marriage and having children but keep investing in bitcoin during amount not make difficult for financial condition. Not bad ideas by spending around $100 monthly for investing in bitcoin but keep priority with family needed or looking other side income become priority for investing in bitcoin only.
Talking about too late or not for investing in bitcoin right not actually still not yet, not problem how much expensive with bitcoin price recently always have potential for bitcoin raising more higher price in the future.
I remember well when many people asking have too late for investing in bitcoin after creating new ATH one month before halving? most of them doubt with bitcoin potential going down after halving but have huge expected with bitcoin success reach up almost 100% from highest price during halving around $73k and right now up to $100k.