The manual transmission is a good choice. It’s generally trouble free.
I have seen some fiesta’s with rust in the rocker panels and hatch/ trunk lid areas.
As with any important purchase, it’s good to know what you need or want. 2011 and 2012 Fiesta were frequently purchased with manual transmission and will be easier to find than 2013 and newer ones.
I have also seen Fiesta’s for sale that have titles marked “rebuilt”. That sounds bad. But insurance companies have been making a policy of branding titles for accidents that didn’t cause extensive structural damage and were really just sheet metal and paint repair. So don’t be too quick to dismiss a potential good deal.
Most importantly, Avoid any cars that have had more than two owners in ten years. Long term ownership usually means that they maintained that vehicle pretty well.
$4,500 to $6,000 should get you a very clean and reliable Fiesta.