My brother did computer refurbs at home and sold them over Ebay for several years. He made very little money doing this, and only a small fraction of what was needed to pay his bills. He was able to keep his head above water because he was living off money from a company buyout from the company where he used to work (computer work). He also took on odd handyman jobs for friends and from referrals by friends, but still wasn't earning enough from the refurbs and the odd jobs to pay his bills. He ended up burning through a lot of the buyout money. Then he lost a lot of money from stock investments that went bad. He had followed bad advice from a friend who advised him to put a big chunk of his investment dollars onto one thing, instead of diversifying his investment cash. He ended up fixing up the house he was living in and selling it, so he could buy a cheaper house to live in, fix up, and then sell that one, too. He continued to do some refurbs and odd jobs, also. He tried to find steady work at companies, but over the years away from the regular job market my brother's computer skills had become out of date. He now does temp work, when he can get it, along with odd jobs, web site design, and the occasional refurb. He is also fixing up his current home for resale, but the real estate market is bad now, and he won't get what the house is worth.
If you are really serious about self employment, you should pick something with a better profit potential. Building or refurbing computers at home doesn't have that potential, so you would still need to do other work to pay the bills. You might consider adding services like debugging other people's PCs, computer tutor work, web site design, etc., in addition to building the computers.
Or you could try something completely different. Good luck with whatever you do.
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau