Aaron,
Before diving in and buying equipment, I suggest you develop a plan.
Regardless of the resources you have available, you are likely to find that ALS will strain those resources.
Military/VA should provide you with a bipap and all associated equipment.
They will also provide you with a wheelchair, help with a wheelchair van, help with altering your home to be accessible.
But, I have found that insurance will not buy me the wheelchair I want and feel that I need. I have to pay for those out of pocket. You may also need to pay additional amounts for a wheelchair van that suits your needs and desires as well as for changes to your house.
There is just a never ending list of things you could spend money on.
That is why building a plan is so important (to me). It is worth laying out what you will need (cane, walker, wheelchair, van, bipap, stand, humidifier, cough assist, etc. etc., etc). The list can be a bit overwhelming.
Then, investigate what will be covered by military/VA. You will find much of it will be covered.
Then, and only then, start spending money on things you deem you need (are required vs desired), but the military/VA are unwilling to provide or cannot process in a timely enough manner.
As an example, here is something to consider about a bipap. I have a Resmed Astral 150 bipap/vent. I have 2 dedicated batteries for it. I have a mounting plate that mounts on a stand. I have the stand, of course. I also have a humidifier for it that mounts on the stand. I also have the circuit I use daily and at least 2 backup circuits at all times. I have several masks of varying styles (nasal pillow for day use and one that covers both mouth and nose for night use). I have spare filters as well. All of this is a system and all must play together. All of it has been paid for by Medicare. From what I have read, military/VA will do likewise.
This system of components was assembled by a respiratory therapist who had more senior folks to call on when things were confusing.
I could certainly have acquired and setup all this myself. I would have had to chase down prescriptions, figure out parts, figure out vendors to order from, return things that were incorrect, etc. It would have been so much more work and would have cost well north of $20,000 (probably $30,000).
Instead, I let my doctors/respiratory therapist figure it out and let Medicare pay for it (I assume they paid much less than the list prices). It made my life easier, got me what I needed faster, and allowed me to conserve funds for things Medicare would not pay for.
I have bought used wheelchairs and am comfortable doing that. If one fails, it would be an inconvenience. But, I only want a new and certified bipap. If the bipap fails, it is much worse than inconvenient for me.
Just some thoughts for you to consider as you navigate this path.
Steve