For Android, you may need to invest more $$$ to benefit from long-term usage.
- Memory: 2GB RAM (minimum)
- Storage: 16GB (or 8GB with External MicroSD Storage)
- Battery life: Android OS can be power hungry, so Utilise power saving modes in Android 5.x. Install apps you need, or restrict background apps. Check the Auto-Sync settings too.
- Screen size/Resolution: Dependant on phone and price tag.
Consider a Nexus for next to no-delay Android updates, as Mobile Carriers may need several months of testing before OTA deployment.
If you do not need an Android phone, do not buy one. Android works best on mid-to-high end devices. As an alternate look at investing into an Android tablet device.