A defibrillator does provide a benefit, but it is secondary to good quality chest compressions. Quick answer: It wouldn't hurt to purchase an AED, if utilized as part of hands only CPR and compression are only interrupted as little as possible to utilize the AED can provide a higher chance of return of spontaneous circulation. If significant interruptions in compressions to use the AED the benefits are negated. If you live further from EMS than 10 minutes and you can afford it buy an AED (the one linked above would be my recommendation). However, I would prioritize a good trauma kit with TCCC approved tourniquets and hemostatic gauze before I would buy an AED.

Edited to add: If you have a history of heart problems (or a cool doctor) you may be able to get a prescription for an AED and some insurances will cover them.