Ask HN:file converting Saas which hosting is the best?

Hello all its my first Saas im doing , simple file converting thing , user uploads document and i start process and convert it to some format then send the link back to the user . my main problem is that im looking for hosting solution that will support this kind of operation . i know i need processing power more then any thing else . also as im just starting i need some kind solution that not expensive for start at list can you please recommend me on such hosting ? thanks!