Niche Clothing line - where to start with manufacturing?

Hi everyone, some friends and I are looking into developing a clothing brand for a particular hobby: equestrians. We are very integrated in the community on social media and in real life and have noticed a lot of up and coming small clothing brands popping up, oftentimes started by people with no experience in clothing or fashion, that seem to be doing very well and growing quickly. The purpose of this project would be to provide a nice side hustle, not necessarily to reinvent the wheel.I currently have my own tech start up so I’m familiar with the ins and outs of running a business and marketing but I’ve never developed a physical product before. I’ve been doing as much research as possible and fell down the rabbit hole into alibaba suppliers.On alibaba I was surprised to find wholesale products matching just about every equestrian brand that’s popular on Instagram right now. Does that mean that these are their suppliers or are they just using the images and the actual product would be low quality? I’m trying to figure out the best way to start up manufacturing with just some ideas and logo/branding.What’s the legality of rebranding existing shirts / riding pant designs? Is manufacturing as simple as reaching out to one of these suppliers that make my favorite other brand’s pieces and seeing if they can develop something brand new? Outside of developing something from scratch, I’ve seen some designs with big “LOGO HERE” text on them, could a starting point be slapping a logo on existing pieces?I’m just trying to figure out what’s legal. Obviously with clothing it’s a bit different than trying to rebrand and sell Disney dolls or something but I was super surprised to find just about all the popular Instagram brands on alibaba and was definitely wondering how much overlap there is between Brand X and Brand Y with similar products.Thanks for any advice on getting started. see hubwealthy.com/wealthy