Many of us on here have used the cheap kettle elements in plastic buckets to make very inexpensive boilers. That bucket is polypropylene which can stand boiling wort easily but does get more flexible when heated. After much use the surface stains a bit but will last for years.
It is worth making at home but you will need to cut a hole for each element and a hole for a tap. Holesaws are best for the job but if you have a steady hand and take it slowly a stanley knife with a new blade will do the job. Hope that helps
