We want to switch from company cell phones to having employees use personal devices.  Thoughts on putting a company MDM (like InTune) on their personal devices?  If so is there push back?  Stipends?

Switching from company-issued phones to personal devices (BYOD) can offer cost savings and flexibility, but it’s not without challenges, especially around privacy, data protection, and user trust.

Putting an MDM like Intune on personal devices can work, but you must be clear about what that means. MDM doesn’t always equal full control. Depending on how it's configured, you can use App Protection Policies (APP) or Mobile Application Management (MAM) without enrolling the device itself. This gives us control over corporate data inside apps like Outlook or Teams, without touching personal photos, texts, or apps.

That said, you need to address a few key questions before you proceed:

• What level of control do you need? If it’s just email and Teams access, MAM-only might suffice. Full MDM makes sense if you need full device compliance (encryption, OS version, etc.), but it comes with more friction.

• What happens when someone leaves? Will you be wiping their entire phone or just corporate data? How do you ensure you don’t lose personal content like family photos or app data?

• Is there pushback? Yes. Employees are understandably concerned about privacy and control. Some worry about you being able to see their location or personal messages. Transparency is key, you must clearly communicate what you can and cannot see or do.

• Should stipends be offered? If you’re asking people to use their own devices for work, especially with MDM installed, a modest monthly stipend can ease adoption and demonstrate goodwill.

Ultimately, the right approach depends on the risk tolerance, regulatory requirements, and the culture you want to build. If you value trust and transparency, you need to find a balance between securing our data and respecting personal privacy.

This is a reasonable request if they are a work from home or a mobile workforce. They need to be able to access their company information while out and about during their work day.
Most modern cell/mobile phones now have the capability to completely segregate work and personal information on the devices. This is better for the company, and the person using their personal device for work. Typically, if you provide information up front that to access company data from your personal device, you need to implement the Work profile. People are fine with it. Explain that it keeps the company from being able to access their personal data and helps them prevent data leaks by keeping their personal data separate. If they leave the company, they don't have to entirely wipe their phone to clear company data, they just disable the work profile, and it leaves the rest of their phone intact. 
As far as stipends go, this is 50/50. Some people don't even think of it. The convenience of being able to use their device that they are familiar with and only carry one phone is fine. However, if you are a larger organization like ones I have worked for, you would probably offer a packaging deal as part of their salary that they get a phone allowance. They are allowed to pick a phone that they get to keep, but they must follow the Work Profile guidelines and are expected to keep the phone in working order. 
If you need people to work at customers sites, or travel for work, and need them to remain contactable, it is reasonably that you supply the means to make that work. 

Using personal cell phones for company business presents several risks, primarily concerning data security, privacy, and work-life balance.  If the company touts itself to support work life balance, credibility would go out the window.

These risks can lead to data breaches, unauthorized access, and potentially damaging consequences for both the employee and the company

I would expect significant pushback. Over the last few years people have become much more aware of data privacy, so what would make them trust their personal data/lives with the companies they work for? In case the MDM provider or MDM Admin accidentally wipes someone’s personal phone, then who is liable for the loss of data?

I’m not sure what apps or settings you intend to manage via MDM, but if you ran O365 and enforced the use of the Outlook and Teams app there are several things you can control directly in the app without MDM on the device.