As my colleagues have alluded to, this is a limiting budget and for any decent lens you will not be looking at a significant lighting rig. Personally, as @KVBarkely said, a good source of indirect natural light is best to give you a soft, even light so you don't need lighting gear. I recently took a series of headshots for a professional group and these are some samples of the results using that lighting technique.
Things of note:
1. I chose a plain, neutral background (I used a mid-gray as it was in the foyer of their building), I was looking for a consistent background - you don't want lots of significant changes in that or clutter.
the indirect light reduced facial shadows and makes people look younger (which you will find older folks like).
2. In my case I was using a full-frame camera with a focal length between 80-130mm - in your case, because you have a crop-sensor camera, which has a magnifying effect, you would select something in the range of 50-80mm.
3. I had the subjects about 3m (10ft) away from the wall, and shot with a focal range in the f/4-5.6 range.
4, I was using auto ISO but limited to 3200.
5. Make sure you have Face and Eye tracking for people turned on in the camera.
So, a lens as has been suggested one of the following, which you can get from the Canon Refurbished Lens Store a) $160 for a 50mm would give you an equivalent focal length for your camera of 80mm:
Shop Canon Refurbished RF50mm F1.8 STM | Canon U.S.A, Inc.
b) $490 for RF 80mm f/2 Macro lens - also excellent for portrait work at a shade under budget:
Shop Canon Refurbished RF85mm F2 Macro IS STM | Canon U.S.A., Inc.
In both cases you need to compose so that you get roughly the torso or bust in view, make sure the camera is level and get the subject to look directly at the lens. I often suggest they close their eyes and I give them a countdown to open them, at which point I take the shot - which makes the pupils of the eyes larger.
Men prefer to be slightly oblique to the camera (although not always depending on light women prefer to face on - it reduces wrinkles.
Take a few moments to talk to the person about their job, hobbies or whatever to make them relax it makes a difference to the muscles of the face and neck. Take several images, not just one.
You will need to do some post processing and if you have a art/marketing department they will likely have software and the skills to complete the image process.
Recon the location and find someone to practise with before the actual shoot to make sure you are not in learning mode.
