The person doing the work should provide a written invoice with materials and labor broken out.

Invoice produced & signed off = payment.

Your property manager should notify them immediately and then pass the invoices on to them as they come in.

We asked repeatedly for detailed invoices and still have not received them to determine how he came up with his costs above and beyond his original estimate. 

Monthly billings fees are @ $5 which is typically paid by the end user (tenant) as a line item on their monthly sub-metering invoice. 

Do you invoice without a tenant shown as a "Job" and leave the invoice unpaid?

I've tried several cloud based accounting platforms that can do this, but most are set up for freelancers with a focus on invoicing. 

With that, more receipts than I can keep up with paying and ensuring everything goes against the right GL and hasn’t been missed.Does anyone know of any software or app out there I can use for my maintenance crews to submit their invoices/receipts that will automate this more for us?

Get detailed invoices. 

Everything is on their invoice.