Might I recommend that you check out vintage (1970s and earlier) Singers? They are quite often available in excellent condition for very reasonable price and will do absolutely marvelous straight stitching of everything from thin silk to multiple layers of denim.
They were designed to be easy to maintain and last "forever".
I have a featherweight that I got in like new condition several years ago for about $400. I've since seen them priced anywhere from about $150 on up depending on whether they have been well taken care of (or refurbished) or they are in need of some TLC (tender loving care).
There are other models which are also well thought of that may be even less expensive. (More $ for fabric!).
Check out the vintage machine section of this board for all kinds of good info.