The selling of ATM puts would require margin.... Which I thought as part of the problem definition said we couldn't borrow money. Not sure if posting margin is considered borrowing as the sale of put would actually result in a credit to your account....
That argument applies to any instrument, though. If you have no money, and also no access to money, then you won't participate in any investment -- so either the answer is the first "best" instrument to get into (most returns relative to ease of access) or the empty set of instruments that cost nothing.
If you are certain the stock is going up, then you can buy Turbos/sprint/MINI ( leveraged certificates). If you are correct in your view, then you will surely make a killing return. And yes..you can participate with small denomination.
perhaps joe the plumber shouldn't be dealing in equity derivatives but rather should be fixing toilets
now if a trader with some capital behind him wants to make money on a stock having a lower bound but having no view on an actual increase, he should sell puts struck at the lower bound with an expiration date as long as he knows the lower bound to be in effect for... otherwise let joe get back to the bathroom where he belongs
now how about this i'll even give you a practical example.. pretty recently the SNB announced they would be imposing a floor on the EURCHF exchange rate at 1.20 by issuing a statement that they would be on the bid for infinity EURCHF at that level - i.e. if you believe the SNB has any credibility, EURCHF can't go below 1.20 (if you don't believe in the SNB that's another story)... guess what everyone then decided to do? sell EURCHF puts struck at 1.20