Combining your company and personal funds in the same account is one of the most common problems of a start up entrepreneurs, this is what we called commingling funds. It can be a serious problem and it leads you to a personal liability for your business debts if this can't prevent as early as now. It's best to maintain a separate bank accounts for your personal and business transactions as well as to keep you books diligently, that's why it is essential to have your company accountant/bookkeeper.
If the business they are building is still on a small scale, I think there is no harm in combining personal funds with their business funds because they can do good bookkeeping so they can know about their business income and also personal expenses, but if their business is on a large scale, of course this is It would be a problem if they combined their business funds and personal funds. It would be better to have two different accounts to avoid problems in their business income and expenses.
Quite reasonable, it is true that if the business they are running is small scale or means not too big in terms of the amount of income then I think I would agree with your assumption, that there is indeed nothing wrong if they mix money from their small-scale business with personal money for their living needs, one of the reasons could be because the amount of money from their business is not too large and they can still make records to just remember that the amount of business money in their personal account is so much.
On the other hand, if the scale of the business they run is quite large, then combining business funds with personal funds is really not recommended because it is clear that the amount of funds must be quite large and cannot be if they only rely on bookkeeping to simply separate personal money and business funds, and yes they need two account accounts to separate their personal funds and business funds. Although the actions of professionals who have known large or small-scale businesses but certainly this will not be too much of a problem if indeed the business they run is still small-scale with the state of the funds they manage is not too large.
For me, i would really be still making out that kind of separation on which it would really be just that be more organized when you do have a business whether its small scale or big scale then having those individual tallies and records would relaly be that much preferrable since you could really be able to easily tracked those incoming and outgoing funds. If you do have a personal acocunt for your personal money then it would be always
best that you shouldnt really be able to collide those funds that came from your investmentj so that you would really be having that a good track with your business expenses and profits on which it is really just the rightful thing to be done on a business if you do really want to see if its progressive or not. You would be able to make out some calculations and preparations basing up on on your sales on monnthly basis.
If you do tend to make some mix up or trying out not to separate then it would really be that confusing specially even if the transactions incoming and outgoing involved small amounts but the quantity would really be that making a mess on which tendency of errors and shortage could be possible.
This is why it would really be that best that you should really be separating those expenses to those business transactions not only just on having that a good track but also
you are really that tending to avoid on potential losses or errors that would be made up. It isnt easy but doesnt mean that you shouldnt really be putting up some emphasis into it.