‘I think it very good for a person to have a lot of working experience’是个简单句,it是形式宾语,good是宾语补足语,for a person to have a lot of working experience是真正的主语.
‘I think it's very good for a person to have a lot of working experience’是个复合句,it's very good for a person to have a lot of working experience是个宾语从句