Been pushing my husband for the past two years and if we'd thought it through a bit further, would have spent more money and gone for one that is battery operated. It is very hard work.
If your town has one, try out the wheelchairs in Shopmobility first, or have a word with the Red Cross and see what's available.
If possible, have a friend push YOU in the wheelchair that you might be buying. I did it and it is quite scary as you feel very vulnerable, and the pavements and road crossing are pretty bumpy.
As a 'walker' you never notice how many paving slabs are broken and how it takes you much longer to cross the road, (but I have to say that in our town of Worthing, motorists are very patient and helpful).
Get one that is adjustable for your height. I'm a very average woman, 5'4, but I spend a lot of time bent over and my back plays up tremendously. If you can, join a Pilates group. It has been a lifesaver for me.
The one we bought, for about £250.00, came with a square 'plastic' cushion, but you could just as easily use one of the cushions from home and it makes it more comfortable for the person being pushed.
Take your time and you'll both benefit.
And if I can make one more suggestion, please thank people whe they move off the pavement for you. This will happen a lot, but if people think their effort is appreciated, they will do it again.