I started in a similar situation; I got 1 Raleigh 20 and 1 Dahon-made Yeah, and upgraded both. Our 1st practice tour was on a level bike trail over a few days, and after that we hit Tasmania which has some big hills and passes. I did a lot of research in advance to know what would be on our path so nothing was unexpected. That helped lots.
The bikes were sort of irrelevant; I just made sure we could ride them without heel strike on the panniers. I used standard racks instead of smaller folding type. With a little ingenuity everything worked fine.
The 2 tours can be found on my page
Jur's cycling photo albums/photo essays, 2nd and 3rd link. Maybe there is something helpful there. The fully loaded bikes were used on the Tassie tour.
Will you be getting some practice in RSA? I bought a lot of stuff online but already had a year of riding experience by the time we started touring. I also built up knowledge in that time which helped a lot. I got super fit by riding to work every day.