couple of things OP.

do NOT use venmo. its for friends. there is zero chance you will get that money back if something goes wrong. the only time i would use it is if i met someone locally and had the part in hand.

while every one else here is recommending paypal (which i agree with). they are leaving a very important piece of info. you can send money two ways with paypal:

-friends and family (like venmo)
-paying for a good or service (which gives you the buyer/seller protection you want).

the friends and family is free for both parties (why no one gets any sort of protection, its the same thing as venmo). the goods and service option is the more secure option. both parties get buyer/seller protection, but the seller has to pay a 4% fee. some sellers eat this cost, some factor it into their asking price at 104%, and lastly some charge the buyer the 4% by adding 4% to their total.

i see the 'add 4%' the most because the buyer/seller protection mostly benefits the buyer. yes, it can benefit the seller, but the main reason the protection is there is in case if the seller never ships your item. ive read multiple times (with zero evidence to back this up), that paypal will likely side with the buyer if something goes south. although i have reason to believe in all of these cases that the seller had no proof anything was shipped; which in that case paypal would basically side with the buyer instantly.

so how can you help yourself so this doesnt happen, or if something gets lost in the mail?

-as soon as you ship this item, mark it as shipped in paypal and include the tracking.
-send an email/PM/text/whatever either reiterating this info, or tell them to check their email for the tracking info (paypal sends you an email when the buyer updates on their end).
-ask the buyer to notify you when they receive the item.
-KEEP THE DAMN RECEIPT. DO NOT TOSS THE RECEIPT. i cannot stress this enough. i have tracking receipts from stuff i sold last march that i just havent gotten around to tossing. i dont know what the timeframe for someone to file a claim against you for, but i recommend you keep the receipts for atleast that time frame incase someone opens a case against you. keeping the receipt will allow you to upload as proof if it comes this far. no receipt = no proof.
-write what you shipped on the receipt. it makes shifting through your tracking receipts a lot less painful.

if you do all of the 5 things i list above. you will have all the proof you need to show that you did your job.

that is basically everything you need to know in a nutshell.