Whether you are simply looking into starting your own business, or already run a full time business from home but are struggling to make ends meet, I would highly suggest getting a part time job for the following reasons:
Depending on when your shifts start, having a part time job can make getting out of bed of a morning unavoidable.
As I am currently working a minimum of 3 early morning shifts a week, lying in bed until eleven is simply not on the cards for me anymore (not that I ever lay in bed until eleven - but I could have done). Being forced to get out of bed early has helped me to get into more of a routine, meaning that even on my days off I still find myself waking up early to walk the dogs, eat breakfast, have a shower, etc. Another reason early morning shifts are the best is because once you get home from work you pretty much have the rest of the day free to work on your business at home. It's very rarely that I want to go back to bed after working an early morning shift.
You will have something to fall back on when your business is going through a quiet period.
Unless you are raking in the big bucks from your business, having a part time job can mean the difference between paying your rent that week or not if your business happens to be going through a quiet period. You don't have to be earning a lot from your part time job, just enough to be able to afford the necessities if your business takes a turn for the worst.
If you mostly interact with your clients/customers via email, having a part time job will allow you to have face to face interaction with other human beings.
Given that most of my own client base is currently from overseas, I don't really get much human interaction with my business unless it's via email or through comments on social media. This has never really been that big of an issue for me as I am slightly more introverted anyway, but I must say that going to my part time job a few times a week and interacting with customers has been a great breath of fresh of air.
You will (hopefully) be able to go on paid holidays without having to take your work with you.
Assuming that you find a job that is permanent part time rather than just casual (although casual work certainly has its perks too) you will most likely be able to accrue paid holiday leave. Without a part time job, the luxury of being able to go on a holiday without bringing your work with you is probably only going to happen if you have been bringing in the big bucks for quite a few weeks prior.
You will have the satisfaction of being able to say that you work two jobs.
There is nothing worse than having someone assume that just because you work from home that you must automatically be lazy. Regardless of whether you sleep in late, forget to shower all day or simply watch too much TV, running your own business - especially from home - is a lot of hard work! As soon as you mention that you work two jobs however, the last thing anyone is going to think about you is that you are lazy. Just watch as you instantly earn people's respect.
These are just a few of the things that I have noticed since starting my part time job. I would love to hear of any observations you guys have made on this topic in the comments section below! :)