I am a college student looking to buy my first mattress. I am 171cm and weigh around 60 kg, I am a side sleeper. I prefer medium-firm mattresses, and I would like my mattress to be under $600. I am only going to be in this city for 2 more years as I will most likely move elsewhere after I graduate, so I do not want to splurge on a mattress that I might have to give away or donate in 2 years. I have read the shopping guide and other information on The Mattress Underground, but I am still very lost as to where to start. I tried out a few mattresses from IKEA and The Brick but due to researching on this forum I have come to realize that those mattresses are most likely not ideal. Any suggestions would be helpful.
Hi Yamify and welcome to the Mattress Underground 
As you likely know, any mattress you choose will be based on your Stats (Height, BMI, sleeping position(s) and any underlying health conditions) - thank you for including these! - and PPP (Posture & alignment, Pressure relief, and Personal preferences);If you haven’t already done so, you might also want to read the the Mattress Specifications You Need To Know and compare these to the Mattress Durability Guidelines to see how different materials ‘hold up’ over time.
Even if you are planning on only using it for the next couple years, you want to make sure you have adequate support. As you are a lower BMI sleeper, you do have a lot more options in the type and specifications of your new mattress.
You don’t say what specific type of mattress you are looking for, or what you are currently using, but the examples you gave, from IKEA and the Allswell ‘Brick’ may or may not be adequate for your needs.
The Allswell Brick, has:
12"
Quilted top layer
Gel infused memory foam of unspecified density or thickness
HD foam of unspecified density or thickness
Pocket Coil with edge support of unspecified thickness, gauge or coil count.
Ikea foam mattresses can, as well, be very low priced but also lack the information consumers need to make an informed mattress decision; any mattress that you look at that does not provide information on specifications of the components or density of foams would set off cautionary alarms for me; a low cost mattress could ‘cost you’ more in the long run if the foams break down prematurely, as this can cause ‘divots’ and ‘ridges’ as well as sagging which could cause muscle aches and pains and even cause alignment issues. For foams, we suggest any foam in a potential mattress has no more than an inch or so of lower grade foams (for memory foam no lower than 4 lbs/cuft for normal range weights, and 5lbs/cuft for higher range weights) and if polyfoam is used, with at least 1.8 lbs/cuft density, just to ensure you have support.
Does all this mean you need to exceed your budget? Not at all! If you aren’t sure what type of mattress you may prefer, you may want to, If possible, try out some different types of mattresses in any local retail showroom just to make a ‘short list’ of those that seem most comfortable and supportive to you, and if you are considering online purchasing, then possibly review the offerings of the Trusted Members of the site, as many of these have a variety of hybrids of foam and latex which fall within of close to your given budget…these have all been vetted for quality, transparency in specifications and materials use in their components, with great customer support and generous exchange and return policies. If you do see any mattresses there or elsewhere feel free to drop in and ask, and we may be able to assess their suitability and support for you!
~ Basilio