The most economical way to keep fit is what your sister did at school
Skipping might sound a bit old school and it is but boxers still do it and many people with limited time, funds and space use skipping and get results.
The Cheapest fitness solution needs almost no equipment
If you have fitness test coming up and need to drop a few kg this is a top way to get into the swing.
Skipping ropes are very cheap, but the cheapest is making your own or even just the hopping and jumping with an imaginary rope will work!
Some things to think about, are you knees though, if you have any knee problems I would suggest riding a bike as the impact is less.
How do I skip? You may remember from school, but if you have never tried here I have a basic video and a few recommendations about how to build up.
How to Skip to lose weight
Starting with just a few seconds and build up over a few weeks to five minuets then 10.
Then hopping from one leg to other, high knee jumps and double rotations.
Over a period of six weeks with daily practice and clean eating, lots of veg and low sugar you are sure to control your weight.