To just start learning about Defenders , buying an 80's LR will set you some bucks back for sure. Once set up right (emphasis on right) and all checked out, they do last without major problems depending on the way they are used and treated. If you can wrench yourself, that would save you $ in the long run. I have owned my '95 D90 going on 18 years now, no major problems, just nit picky ones at 80K mileage, but then again I treat and care for her like a mistress
When I bought the truck it was practically new with very low miles.
All the defenders are pushing some years now, and upkeep would be on par with classic cars, not to mention the initial investment to make her right will be expensive.
I feel a better solution if you must have a LR, would be the 60's70's series LR, much simpler electronically and mechanically, and would give you a foundation in all things LR as a hobby.
(My first LR was a '67 series 2A nearly 30 years ago, after 4 years I got a 80's 110 defender 3.5L, then a 90's RR, then graduated to the 1995 Defender.)
Series are awesome off road stock or with parabolics. However HWY driving is like being on Safari on steroids even with an overdrive unit. (drove from NY to LA and back with the series, didn't break down once). That would be a good start IF
you were to keep the Toyota as well for daily runs..