Now we know that we can’t have a guitar with the best features for 500$ or less, let’s focus on the fact that there are just two type of guitar you can searching for: New or Used.
What you have to sacrifice in this section can be: production, hardware (almost 100% of the times) and manufactures. The more you go below the 500$ mark, the higher is the risk to find bad wood and made in China guitars. Expecially for the new pieces is very common to find a guitar made in Asia but as said before it’s not always something bad if you are searching low-budget guitar.
Epiphone or Squier? You must be very lucky to find a well manifactured guitar for these two brand. You must sacrifice details, production and almost every time manufacture. These brand are linked to the bigger ones just because of an economic choice of the mother house to give to normal people a cheaper version of their most exspensive guitar. The really minefield of all this post is the range of price where you can find both “Epi” and Gibson, Squier and Fender. For what I’ve experienced the differences are in the details and PU. So, if you want to spend 100$ to have a “better” bridge, color of body or bridge PU you are free to choice the “big brand” guitar but you have to know that in both cases you don’t have a very good guitar. Online you can read opinions about the “melody maker”, “junior” and “faded” series of Gibson to know what they sacrificed to give us, for a modest price, a guitar labeled Gibson which has almost nothing of what makes Gibson a top brand in guitar production. So what's the main "pro" to buy a cheap guitar with these brands? You can sell it for half the price and so to have virtually paid it the half, when you will sell it.
My advice for Epi and Squier is to find a good series. Almost every two years Gibson and Fender produces a new series with new features that change mostly details, but the big differences are the production and manifacturing because in a rare case you can find an Epi produced in a decent factory in Korea and this means that its overall quality of manufacture is higher than the others. Online you can read a lot of debates about almost every series of Epiphone/Gibson, Squier/Fender to decide what’s the best year of production of that specific model.