The beginning is hard. Getting organized is a never ending challenge. If you plan to continue growing your rental portfolio then get Buildium. You'll read the "i can manage it for free in spreadsheets" a lot here, which is true. But make the investment in your business now to create a foundation for you to grow upon.
Buildium will be a life saver for your rentals. Take the time to set it up. E-leases, use the accounting, get all documents uploaded, online payments, maintenance, etc.
Sit down with a bookkeeper or cpa, get your construction books setup in Quickbooks. Use Buildium for rentals. Keep your books and accounts separated. Remember your books don't need to be crazy detailed and complex, Buildium will keep the details of your rentals and you will cost segregate rehabs outside of your books.
Set-up files in dropbox, Google drive, or whichever cloud storage you choose. Setup Gsuite, create an email for your rentals and one for your rehab biz. Have them directed to different folders. This allows you to manage your email contacts from one account.
Get flipping spreadsheets. It's $200, set them up with your costs. I've completed $200K remodels using that spreadsheet, it works. Create a separate spreadsheet for selections. Have description, cost, sku, vendor. Your rentals should always be exactly the same, paint to house numbers.
For rehabs you combine the venture sheets with your selection spreadsheet to create a project workbook. You can do this by creating pdf's or you can print them, put in a binder. Doing a tile shower? Make a quick drawing of the design, add it to the workbook for quick reference. If you want to go digital and plan to really grow the rehabs then check-out co-construct.
Whatever you choose, just create the framework to operate in and continually improve upon on it.
Real estate is conceptually very easy but more difficult in practice. Particularly the construction aspect of things. Keep grinding, always be working to improve the system, and don't forget to look up or you'll miss the bigger picture.