Fitting a sidecar to a solo bike is a lot more complicated than it first appears. Having someone who knows how to set up an outfit.
The outfit needs to be set up for tow in, handling, etc.
How far forward or backwards the sidecar is positioned on its adjusters, in relation to the bike, will affect the handling.
For instance, I had to, with the help of a equally knowledgeable friend, move a sidecar's main frame mounting spar 7 Inches further backwards (this moved the sidecar 7 Inches forwards) so that the oufit would stop dragging and veering to the left as the bike's speed past 60 MPH, due to wind resistance.
On a well set up out the whole rig should steer dead straight, without turning, when the rider's hands are not on the bars.
If a solo bike has an MOT it will not be valid once the sidecar is added, so a new MOT test will be required.
I own and ride an outfit, as do some of my friends. One has a bike carrying rig on a special flatbed sidecar.
On a good note is the fact that sidecars are still covered by the 1929 Motorcycle Parking Act and are therefore not allowed, by law, to have a parking fee charged for parking space use.
If you've never ridden an outfit before then best find someone who has to show you the ropes and explain some of the new handling jargon you'll have to learn and cope with.
One can either climb onto an outfit first time and ride OK, or the thing will try to kill you.
It all depends on how good a solo rider one is. Point and squirt idiots or riders who ride on the brakes all the time, will have a terrifying time on outfits.
Good riders will have no trouble at all adapting to a third wheel.