I have a stock of cellos available for rental at just £40 per quarter. Renting a cello for your child means you won't have to buy several expensive instruments as they grow or that you can try learning before buying an instrument outright.
My Cellos are usually either Stentor Student II or equivalent Primaveras. Each cello is correctly set up meaning that your child (or you) will have the best chance of making progress.
Cellos from 1/10 up to full-size can be rented (subject to availability.) If you don't know what size is needed then I can measure and advise you.