Quote from: kenw232 on November 16, 2017, 07:53:23 PM

...I do not want want to borrow money to buy more bitcoin and have to pay interest and worry about a cut off price (eg. BTC drops to less then 50% of your trade its auto-sold)...

You will not find a service that offers margin trading without margin calls. These two are mutually dependent.

Besides, it is highly unlikely that you will find a service that allows you to take up margin positions without paying interest.
Most brokers charge you for the money you lend for margin trading. In most cases the capital is put up by the broker themselves
or some entity in the background. In the BTC world there are a few other models where you are borrowing from other users
(e.g. Bitfinex and Poloniex). However, all mentioned options have in common that you pay interest for open margin positions.