I need advice as someone wanting to get into VHS collecting

I (14M) really want to get into VHS collecting, and would appreciate advice from people who have been doing this for a long time. I felt the need to mention my age as going to shops alone and other things like that I'm not able to do, and I'd need my parents to fund anything. I already have a small DVD and CD collection, and the main reason I want to get into VHS collecting is because one of my favourite shows (The Magician's House) never got released on DVD and I'm only able to watch it on YouTube because some random person reuploaded it. I'm nervous that it will be taken down, thus why I want the physical copy. I've found it on VHS on eBay, but that's only one series. Another series I'm desperate to watch (Rentaghost) was first released in 1976, but I can't find the VHS copy on eBay. If not on eBay, where would I be able to find VHS tapes? Charity shops are good for new finds, but looking for something as specific and old as Rentaghost is very difficult. I know the rules say that posts like 'looking for x series' are meant to be put in the Buy/Sell page, but I'm not asking that, I'm asking how to get into VHS collecting in general. Any advice would be very helpful and highly appreciated :)

TLDR: I want to get into VHS collecting and don't know where to buy tapes, and I'm 14 therefore can't really go out and find places by exploring.