When downpayment, etc. is a crunch, you can try with FHA…they will do a multi-unit up to 4 units if you owner-occupy one of the units…VA will also if you have that benefit…these are low-down payment programs.
lenders typically take 75% of your gross rent and figure that as income; of course on the other side of the balance sheet you will have a mortgage; thus a rental can either hurt or help your DTI.
finding rentals that are solid cash producers can be tricky. even good properties will have months where they consume cash so actually $$$ into your pocket can be a bit lumpy.