Yes, yes and YES
Hopefully, that is all you need to hear. If not, let me elaborate (but be warned, we will come to the same conclusion - just after a lot more words).
Why Buy the Segway
Now, you're probably going out and selling all day because you want to make some money. Odds are that your bank account is looking pretty sad right now and you're looking to make it happy again. So why buy an expensive scooter - if anything, it is just going to strain the bank account more. Right?
Honestly, that is what I thought when I started my first summer. Figured that I could run from door to door and get the same effect for free. Even better, I'd get in some exercise as well. It was kind of free (but not free if you consider lost earnings) and I got way more exercise than I wanted.
Luckily (and unluckily), my buddy who I had gone out with had decided about two weeks in that selling pest control door to door was something he had no desire to do. He had won a Segway in a rookie training competition a few months earlier. Back then, a new Segway was ~$900. He offered his slightly used Segway for $450. The Venmo hit his account 5 minutes later. One of the best uses of my money that summer.
That Segway was a great investment because it helped me to hit at least 5% - 10% more doors each day. Honestly, likely closer to 20% more doors each day. I definitely got at least least 2 to 3 extra sales a week because of my Segway. And that is being conservative. With my ACV and commission, that Segway probably paid itself back in the first week.
If you're any good at selling and are going to stay out for the summer, it is VERY WELL worth it. Here is some back of the envelope math:
Assumptions & Results: You hit 100 doors a day, you sell 5% of the doors you knock and you make $200 a door. If a Segway lets you hit 10% more doors a day, that means you'll make an extra $600 a week (60 more doors a week at a 5% close rate is 3 more accounts a week - at $200 an account, you get an extra $600 per week). At 10 weeks a summer, that's an extra $6,000 a year. With Segways costing closer to $600 now, that is a 10x ROI. I wish I could invest in more 10x ROI opportunities. If I could buy you a Segway at $600 and get a 5x ROI, I'd be all over that.
Which Segway
Now this is important. You should be careful about the Segway you buy. Ideally you can get the Segway Ninebot S2. You can find it here and here. (These are NOT affiliate links by the way.)

Unfortunately, the S2 appears to be sold out a lot of the time (like it is in the picture above). If that happens to be the case, you should check out Facebook Marketplace and see if you can find an old Segway S Plus - it will likely run you back $300 to $400. Well worth the time and effort to find one.

Do not get an Onewheel, do not get a cheap hoverboard, do not get a scooter. You want a handsfree device. The Segway is literally the perfect device for anyone selling door to door.
Is It Hard to Learn?
Luckily, no. The Segway is very easy to learn. Took me about 20 minute to get the hang of it. Honestly, my balance is not great so it is likely to be even faster for you. Segways are just easy to get the hang of. After my first day, I was very capable of ripping on the Segway. I've probably done over 2,000 miles total on my Segways since then and have only crashed once.
A Brief Ending
Well, I used way too many words to say it, but the answer is yes. Please get the Segway. Please give yourself the ability to make that extra money. It will be well worth it. Yes.