I want to photograph in low light settings and make 11x15 enlargements, current smartphone not adequate

Look for a second hand Nikon or Canon. With Christmas just past there will be a flood of them on the market from people who got a snazzier camera from Santa.

In particular you want one with an f/1.8 f/1.6 or f/1.4 lens. This will maximize your light gathering capability. This won't have optical zoom, but most zoom lenses that come with with entry level cameras will be f/3.5 at best. This is about 1/12 the light gather capability of an f/1.4. When you can afford it there are some good f/2.8 (one stop faster) zooms.

Read reviews. You may find that an older full frame 12 megapixel camera has better lowlight performance than an newer APC beginner camera. In general larger sensor sizes will do better in low light. Newer ones also do better, so there is a trade off.

Locally I found a Nikon 3300 with a f/1.8 lens for $425 Canadian, which would be under 300 US.

Try ebay also.

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A commenter pointed out the 11x15 print size, which I didn't take into account.

No phone is going to give you acceptable sharpness at 11x15 even in good light conditions.

Indeed, if this is a solid criterion, then I suggest that you try renting a full frame camera, and an f/2.8 zoom.

300 dpi is about the coarsest you can go and not have visible dots. For comparison color newsprint is about 150-180 dpi. National Geographic is something like 600. (These figures are dredged out of a very deep, but ancient box of trivia in my head. Commenters will set me straight shortly.)

300 dpi * 11 inches means that the short dimension of your image has to be 3300 pixels. 20 Mpix will manage this, but you will have to crop tightly.