That's cool, I didn't know you could rent them. I'll have to check that out.
I rented one with my first as I had a very tough prgnancy bleeding from 7 weeks to 17 weeks. The rental company went out of business so I still have mine and have gotten a heartbeat 8-9 weeks on all 3. I think renting is the way to go if you can.
I don't know where you are located but here in Colorado a lot of clinics rent them out. The cheapest I have seen in 20 dollars a month.
With our last pregnancy we bought a very inexpensive one and it never worked for us : ( but I guess you get what you pay for... I love hearing the heartbeat and would have loved it if it had worked.
I looked into it but most of them were $90 or more, the nicer ones with better reviews costing upwards of $150. You can get them at Walgreens.com and Amazon, but good luck finding one for $50. If they weren't so expensive I'd get one, lol.