Welcome to BP @Dan Mackin While I do not have a lot of posts I have learned a lot from the BP community! My wife and I live in Firestone (10 miles from Erie) and have just purchased our first rental home. Actually, just closed yesterday and have the signed lease and first months rent and deposit the same day with our first tenants. With my wife as our realtor the buying process was not scary.......but screening and going over the lease with the new tenant was a different (exciting) experience. We feel BP really prepared us for this.
I agree with @Tara Hall you have to invest in what you are comfortable with and what you are looking for in an investment. For example, renovating a home in old town Erie could take considerable work on an old home. Will you do the work yourself or hire contractors? Do you have experience managing contractors, etc.? There is a lot of information on BP so just search for it.
Living in a property with an accessory dwelling is a great idea, if you don't mind having a tenant so close to you. Just depends on what you are looking for, what your goals are and comfort level.
We have looked in Erie for our primary residence and rentals and have found (I am sure you know) that even though old town is in Weld County, the west side of town (west of County Line Road) is in Boulder County which our experience has shown has higher taxes and different regulations if you are in unincorporated Boulder County vs. unincorporated Weld County. Just something to consider.
Keep us posted on your thought process and what you choose. I am fairly familiar with Erie and have done some work in the Town (Erie Library). We are so close that if you ever want to get coffee and share ideas send me a PM.
Set up key word alerts and search for anything you have questions about. The information is on BP.....you just have to find it.
Good Luck!