Reptiles, as adults, tend to be very inactive.
Bearded dragons entertain children whilst they are little, when they are bigger they sit in the hot spot, eat and Poop.
Royal pythons, sold as starter snakes, are temperamental. Any changes to heat, humidity, enclosure design, excessive handling and they go off food... For months at a time.
Reptiles, if kept correctly live years, one of my snakes is 30ish years old. Beardies lived for 8 years, torts/terrapins are very long lived.
Also you have to consider the cost of electric, some reptiles require a heat lamp and UV. UV needs replacing every 4-6 months. You'd be looking at running these 12 hours plus a day. Plus daily supplements for some reptiles and daily food.
Reptile vets are few, and some charge a fortune.
A wooden viv, which will need replacing every 3-5 years, depending on humidity levels, costs £150 plus depending on size.
UV tubes cost £20 plus depending on size, heat lamps from £10 plus.
Insects cost £2 plus a tub and some will eat 1 tub a day, plus veggies.
What ever reptile you chose you will need a thermostat, otherwise the animal will cook itself.
Hope that helps, pm me if you want any other info.