The first home I bought that I intended to rent out and later decided to sell took me nearly 3 years to fully repair. Thankfully, it was still considered a livable space so my wife's cousin was staying there every summer and giving me some "rent" money for it. There was so much work that needed to be done that I couldn't afford it all and had to work on it here and there, taking a few months off in between.
About 5 months. I work fast and don't typically buy homes that require a lot of work. I have only just started investing in such a thing 2 years ago however so I have only purchased and sold 3 homes.
Never. I don't buy to rent or resell. I just work with homeowners and homebuyers. I have had a couple that kept doing more repairs to their home to bring the price up. It was a process that lasted nearly 9 months. We joked when it finally sold that it was like giving birth.