I did Keto for a month in September. It requires a good deal of self-control to stick to it (you'll quickly realize that only about 1% of the grocery store is food you can eat on Keto - resisting that temptation constantly is a trial) but it's not particularly expensive. You do have to be "in ketosis" to get the full benefits of Keto, but I've also found that just sticking to a low carb diet (under 100 carbs p/d) is a good start to ease into it. For Keto you will need to stay under 50...some people stay under 20.

I lost about 15 lbs during the process and my diet mostly consisted of salads with lots of chicken + cheese + high fat dressing. I was a vegan before I switched to Keto so eating my veggies was not difficult, but some of my friends struggled to keep a "healthy" diet during the process.

The most difficulty you will have doing Keto is your own self-control. Finding recipes & food to buy is easy.