Hello!
Im sorry to write this but there is no posibility to make a profit on a restoration of a car as popular as a 126!
If you do go that way its best if you do this whit out any savings on the parts material ect. Becouse
after you sum up the cost the price 4 your 126 will be enourmous ! So no one will buy it , so you want to have a car thats made good becouse you will be driving it 4 a long time. Dont want to be rude but after few years of working whit old cars i kinda now the story on my own example.
There is however a way to go 4 you. Do it the whelers dealers way. Buy cheap, do some minor repairs, polish the paint job and sell !!
Any way, wish you luck, and hope i can help !