It's as safe at bitcoin so you are sure to get your money back.
I offer some loans sometimes and I only accept big volume altcoins like litecoin, dash and Ethereum.
Most other altcoins I don't accept since they are not listed on my exchange.
What happens if the price of the bitcoin rise, and those altcoin price drops against bitcoin even though their dollar value remains the same?
it has happened already but it is very rare and not for the top altcoin, since some of them are directly tied with fiat like bitcoin