I did a comparison between renting out a terrace house in malaysia and a flat in Singapore. Furnished and unfurnished. ROI more or less same except slightly lower for some parts of JB. Except one in Ringgat and the other in Singapore Dollars. As usuals, those with beds, electrical appliances, oven, water heater, washing machine etc...commands better returns, both same for JB and Singapore.
1 hdb flat is about 2.5 terrace house in JB. But rental return of 2.5 terrace house is also equivalent to a 5 room hdb flats. There are only 2 differences. 1 is hdb is 99 year lease while jb terrace is freehold. The second difference is that for Singaporean, hdb flats can use CPF to pay, whereas terrace house in jb can only use cash.
So my verdict is that if can't invest in condo in Singapore, better start small in jb first.