Great points made above.
Also depends on what journal you're aiming to submit to. Many don't take this into consideration during the manuscript process, but that's extremely myopic IMO. Journals have biases, traditions, and editors following past conventions, plus some more. Bad writing (due to inexperience, most often) is often overlooked as a factor of why papers with okayish experiments and conclusions face trouble being published).
If your target journal is pretty down there and you're just publishing to get it on a med school app and don't really care anyone reads/cites it and actually adds to the literature conversation (cynical view I realize, but c'mon let's be real; we know this happens), you can afford to spend less time writing and making it good. Obviously, the higher up the ladder your target journal, the more time you should pour into rewriting and revising, which is the only way to ensure great writing, asking other professors for comments, and so on, before submitting.
Like the others said, if it's your first time, it's gonna roll up your balls and smash them to smithereens to get it done well. My first group paper took 10 months from data cleaning to submission, accepted at JACC (3rd in cardio). My two PIs are all writing monsters who rewrite an average of 25 times for a potential high-impact paper, and those are the ones that have made it to JAMA/BMJ/Annals in the past. Some 5th year (MHS year) med student got his done in around 3 months and only ended up in BMC Med, but it wasn't like his research was any crappier than most, which is why I strongly believe in the writing quality factor.