How to learn violin the easy way.
All you need is an ukulele (or any other small four-string instrument). Ideally the distance between nut and bridge should be about 32,5 cm, if you are going to use violin strings. Then you tune your ukulele as if it were a violin (E, A, D, G - from bottom to top). If you already play the guitar, you can learn the violin by yourself. After you get familiar with violin fingering, then you can buy a violin and start to learn how to use the bow and other things. This was how I learned the violin and the viola.
Even after you are proficient in violin/viola the ukulele will be useful to practice new tunes. I still use my ukulele because it is much handier than a bow instrument -- I can play it even while lying in bed.