Bhai jan muje vitz lye hue juma juma aath din hue hain hehe I am not expert, well what I have observed from this thread some vibration is normal like I personaly experince when I am in "D" and apply breaks to stop car for few moments car give light vibration but then become normal
If ur car giving more than that vibration then most probably car needs some tuning like replacements of plugs or atleast cleaning and adjusting the gaps of plugs, change of airfilter , throtle body cleaning etc
To me its not very serious issue
Share car pics here so experts can judge the car condition and suggest you reasonable price
What's his asking price ? Car interior condition ? Exterior condition like how many panels re-painted? Secratches, dents , rust if any ?