Bulging drywall, should I still buy? My 1st rental

[Shao Ya Xu]

Hi everyone, I am in the process of buying my 1st rental property and just finished with home inspection. The only thing that worries me are bulges on the drywall at three different spots cause by leaks. Two spots are near the window and might be cause by a gap between the aluminum trim and window outside. The other might be due to a clogged gutter that cause water to overflow back to the roof and down the wall. According to my contractor, the fix to prevent further damage seem to be simple, seal the gap between the trim and window, clean the gutter, and replace the drywall on those areas if needed. But I don't know how much damage the leak has done , such as possibility of mold (but I didn't notice any musty smell). The property is sold as is. Below is a snapshot from the inspection report. 

So how worry should I be? Anyone encounter a similar problem before? How much did it cost you? Thank you so much for your feedbacks!