I'm not familiar with the brand, but it looks like a fairly basic specification.
Without wanting to be too negative there will be some downsides - it'll be heavy and the basic components will probably not work as well as better ones (for example, the wheels probably won't roll as easily as ones built on better quality hubs). I'd want to check that everything works before parting with any cash. Does the seatpost adjust up and down / do the brakes work / do they need new blocks or cables / are the wheels true? etc etc. You could end up spending as much as it costs (or more) on new bits if it's not in serviceable condition.
On the positive side, if it works and you can get it cheaply enough it'll do the job.
Regarding size, I'd strongly recommend trying it and seeing if it feels right. One manufacturers 18" can equal another's 17". You also need to be comfortable with how far away the handlebars are, the saddle position and so on.