Well HEMA wasnt a thing beyond olympic fencing until recently, fencing used to be a general term for sword play and found its peak popularity in the renaissance, one of the great masters from italy, Fiore dei liberi recounts his journey across lower europe teaching fencing to nobles who would participate in knightly games for honor or sport, while he is hardly the greatest master (the best schools came from germany in the lineage of liechtenauer, no doubt) he has an interesting story and presents his treatises in an incredibly friendly manner, it reads almost like a children's book and is a good system for absolute beginners, vid related, inspired by his bouts against rival schools and his proposed training scenarios.
That being said, I also do not have a school near me, so when i was a boy I began to teach myself, I started funny enough not with Fiore's child-friendly manuals, but instead with those of the german school of liechtenauer, and now study nearly exclusively with meyer.
Joachim Meyer was a German fencing master in the tradition of johannes liechtenauer, and probably the best source for longsword, dussack, pole weapons, rapier, and dagger, he assumes you are already familiar with the weapon, and so goes into great detail in his books, from grip to thumb placement to footwork to how low you should squat (dude loves leg day, so get ready for that), he also provides invaluable diagrams for footwork and striking (the meyer square is a brilliant teaching tool).
So how do you read his manuals? Well you could spend 30 bucks on a book, or you could use the totally free wiktenauer.com (specifically wiktenauer.com/wiki/Joachim_Meÿer) and either memorize, save to your phone, print out, or my suggestion: rewrite the entire thing with diagrams.
Sacramento Freifechter is a pretty nice youtube resource to supplement, Theres another good resource out of europe that i for the life of me cannot remember right now, and will post later if it is recalled.
I should note that If you are interested in zweihander/montante/spadone, look for figueiredo's memorial da prattica do montante (the memorial of the montante, MS 49.III.20.nº.21) While the two handed swords are generally used for war and operate like pole arms (most famously by the landsknecht), in the iberian peninsula they rose to prominence as body guard's weapons, figueiredo's treatise is all about fencing multiple opponents at once, and even doing so while having to defend a lady, he gets so specific that there are moves entirely designed for alleyways and gangplanks.
What youll need
-A copy of some sort of fencing manual, on computer, phone, book, etc (free-30USD)
-a waster or feder, though if you do not have someone else to fence and the proper safety equipment, feders are a waste of money next to stage steel swords and wooden wasters. You can also use pvc warped to have blade/flat/quillon features ($5-$300USD)
-A Meyer square to practice with until you memorize it, can be painted on a wall, board, newspaper, etc, can also be printed on a poster (basically free - however much you want to spend)
-A Meyer circle for footwork, could even be drawn in dirt with your foot, or in chalk in a driveway, on a porch, in a garage, etc (if you pay anything for this youre doing something wrong)
Thats seriously it. Having a partner both improves and complicates things though, in that case, depending on your choice of material for your sword, youll need to take precautions when fencing.
Against foam - no protection needed, larpers do this shit all the time
Against unpadded PVC - eye protection, like shatterproof goggles throat protection is desirable
Against waster - same as pvc, though head protection recommended for harder woods, fencing mask is ideal, shin, knee, and elbow protection are desirable, throat protection required if you use thrusts.
Against Feder - Fencing mask required for serious, full speed freeplay, absolute force sells a 3W (three weapon, meaning rated for all three olympic style blades) mask for 60 bucks, this is also good for wasters, If you want to spend a little more money, a helm of at least 16 gauge steel can be substitute, and usually cost 100-150 bucks, when using wasters I wear a sallet as the waster isnt thin enough to enter the visor. While fencing masks will come with throat protection, a helm generally will not (burgonet being an exception, and quite a beautiful design too) and will require either an aventail, a bib, or a gorget.
If i left something unanswered feel free to ask.