It is true that ordinary people can also start investing by making simple calculations, starting and starting with managing it in the right way are not the same thing. But if you want to make your investment safe and grow or if you want to keep it safe for the long term, common sense alone will not work. However, it is important to gain knowledge to increase and keep your investment safe in the future. Anyone who does not have this knowledge is not really qualified to invest in Bitcoin. Starting work is easy but completing that job correctly and on time is much more difficult than starting.
Anyone with available discrietionary income should not wait until they have gotten all the know before they can start... Gaining knowledge in Bitcoin is a gradual process, that is made possible through actual involvement that is why it is much more better that folks kickstart their accumulation journey and then learn gradually as they go...
What is the total expenditure of the family and your own income, How much is left after paying all the expenses and is it safe to invest in Bitcoin with that remaining money, these can't be calculated or considered with just common sense, but to do these things, you have to write down the total income, deduct the necessary expenses and then determine the remaining money.This is at least a matter of basic budgeting and math.
Are you sure you even know what common sense is, coz from the way you are talking, you sound like someone who is actually confused about what Common sense really mean... Common sense is like your Faculty of reason, why guides majority of our actions... Even if you write down our expenses and whatnot, it is a through common sense that you can be able to know those expenses that are essential and which one needs to to be cut off, and it is also common sense that can be able to tell you what is actually available and safe to invest with... Writing down on the paper or better still budgeting dosen't make decisions for you, it is common sense that Helo make majority of decisions...