Lots to cover here, and others will have far more experience with this than I do, but I'll pass on what I've learned over the years...
First, pick the kind of bike you want to track. I'd strongly advise against anything with big power, unless you have a LOT of experience, simply because you'll learn a lot less babying a litrebike than you will improving lines and corner speed on something slower. Lots of folks track the newer 300/400 parallel twins and have a blast doing it, and if you want a bit more torque, an old classic is the SV650 for a super reliable and fun track bike. There are also 600s, but most make well over 100 hp, or you could go with a Triumph Street Triple 675 and strip off the lights for a very fun but different approach.
(I went with an RC51, partly because I'm a big guy and wanted more torque to haul my lard-arse out of corners, partly because I am of the age where that bike is part of a Honda race lineage that I think is the coolest ever, and partly because Honda build quality of the era is second to none. It makes about 125 hp at the wheel after some very light tuning, but has a super friendly twin power delivery and weighs as much as a tractor to keep things planted and really make me sweat.)
BUT, the (sort of) mistake I made was buying a beater street bike and converting it to a track bike. It was huge fun to do the build, but it ended up costing me far more than just buying a ready-made track bike would have. I can get some of that back if I were to part it all back out again, and I have the peace of mind that all track miles on the bike are ones I put on, but I ended up spending over $10k for a bike that would cost no more than $7k if I sold it as-is.
Items to consider on the basic end of a track conversion include track fairings (not cheap), new chain and sprockets, braided brake lines, clip-on bars, crash protection/sliders, and track tires. Probably suspension, too, but it depends on the quality from the basic bike (e.g. a 675 could get by with just a rebuild and maybe springs, while a stock SV650 could need a whole new shock and fork cartridge kit). From there, the sky is the limit, with exhausts, fuelling, engine work, slipper clutches, upgraded brakes, lighter rims, and on and on and on.
Much cheaper and quicker is to just pick up a bike someone else has already done the work on, ideally with as stock an engine as possible, track fairings that are well made and not explosive plastic from Ebay, and most of the details sorted. There's a Facebook group called Track Fanatics Canada (
Log into Facebook) that has the occasional decent track bike go up, and they tend to be more likely to be a solid bike over a random Marketplace post because the track community in Canada is small and many know each other. In the end, though, it's always a gamble as most track bikes have done a lot of hard miles and issues can always come up. If you have a spot and the inclination, repairs are always possible.
The safest bet will be a bike that's already reliable with a low-stress motor, like the SV650, and with ready availability of parts and advice. One issue with the RC51 is it's rare and old enough that getting certain parts can be a challenge and require a lot of internet sleuthing. Bikes like the SV650, on the other hand, are everywhere on the track, parts are easier to find, and there's a ton of resources to help with any issues that may come up.
As for renting vs buying, I wouldn't rent more than a couple times if you have to. You should be able to pick something up for a few thousand, and if you don't use it, you can sell it on for most of what you paid. Track time is already expensive, doing it on a rented bike is even more so and will be limited to more training and far fewer dates etc. Maybe there are rental services I'm not aware of, but the risk would be stratospheric, so I'd be very surprised if there's much that isn't tied to supervised training...
