Keep personal and business finances separate to create less headache.You should also do the following to make your bookkeeping easier:- File all receipts in a dedicated Google Drive folder.

Besides putting together the best SOW using accurate/actual quotes as @Peter Mckernan and @Alan Asriants commented above, another key aspect is tracking expenses (bookkeeping) and monitoring the budget throughout the project. 

I like to use Stessa for bookkeeping but not for property management.

I do my own Bookkeeping for my businesses and my clients and recommend him as a General Tax Accountant.

I use a CPA, too, but I like to do my own bookkeeping throughout the year and send him a tax package quarterly to review.  

More convenient bookkeeping 

I created an electronic google doc time tracker: Time LogContemporaneous time log of rental real estate activitiesActivity DescriptionTenant recruitmentTenant screeningNegotiating and executing leasesOverseeing repairs and maintenanceCommunications with tenants and vendorsTravel timeResearch for potential rental real estate (pub 925)Acquiring rental real estate (pub 925)Paperwork/bookkeeping/bankingResearch and purchase of materialsRent collectionEvictionOn-site cleaningBill paymentOther:Time SpentDateMM/DD/YYYYSubmit

I do my own bookkeeping for now and rentals are in my personal name. 

He is also doing the bookkeeping?

Buildim has a general ledger so you can record credit card transactions the same as in any other bookkeeping software 1- add to chart of accounts a current liability called for example capital one credit card2- when you want to record a credit card transaction go to general ledger create a journal entry, for example if you swiped your card for a maintenance expense in the amount of 1,000  youshould debit maintenance 1,000 and credit your liability account called capital one credit card for 1,000so your liability account balnce is always the same amount as your credit card balance 3- if you pay intrest on your credit card add to charts of accounts an expense account called capital one intrest fees and when you got charged intrest create a journal entry debiting capital one intrest expense account and crediting your liability account 4- to record a payment to your credit card you can record a check from your bank account payable to capital one you should add them as a vendor or you can do a journal entry It simple for anyone with a little bookeeping knowledge and btw thats how its also done in quickbooks or anywhere else And thats the correct way doing it although there are a few other workaround ways for exemple creating a contra asset or as paying a vendor So i dont know why you blame buildium it would be the same with any other software