How do you pay the other expenses; repairs, maintenance, property management, capital expenditures?  

Make a spreadsheet and take your total rent and subtract vacancy, mortgage, capital expenditures/Maintenance, Tax, insurance, and property management (You always want to include this just incase down the road you end up using property management).

that doesn't account for vacancies, or capital expenditures.

However, once you move out, your cash flow should be around $350 - capital expenditure/month. 

Once you have enough cash to buy a home cash + rehab + capital expenditures, you can BRRRR/flip over and over. 

Please offer your advice on the best place to purchase these large capital expenditures.

I am allocating roughly $100/month per unit to go towards repairs and capital expenditures. 

Debt is allocated by tracing disbursements of the debt proceeds to specific expenditures.

Gross Income $1,900- PITI= $700 -Vacancy($100)-Management($190)-Water/Trash($60)-Capital Expenditures($150)- Repairs($100)= $100So only $100 in cashflow after all those expenses which is not ideal BUT have been cutting costs. 

But the property turned out very nice and we are happy with the updated/upgraded systems of the house and should have limited capital expenditures upcoming for a significant amount of time.