When investing in real estate rental price checks help avoid investing in bubbles. No investment strategy is perfect. If you invest in a new area early, it can be that rental prices do not yet reflect long term value (say rental prices near an announced MRT station but one that won't actually be in service for 5 years). But ignoring rental prices is risky (just believing long term things will keep going up - this was a big part of the problem in the USA bubble - prices way out of line with rental values).
For this reason, I am skeptical, of investing without rental market checks. It is also true I think it is not yet a fully functioning rental market in these new housing estates. It will likely be at least 3-5 more years to get a decent idea of where rental prices will be going and how much rental demand there is.
Properties can sell to investors from Singapore (and many other places) that buy the properties to use as vacation homes, retirement homes... for there long term plans). This can even be sustainable over the long term (a significant portion of units bought this way) BUT it is much riskier as an investment than if the units bought for investment are rented out and a fair market rate can be determined to evaluate purchase prices.
To me the key to the investment potential of JB real estate is most importantly, JB having jobs that allow people to buy or rent these houses. It seems to me at the current time there are not enough of those jobs. The second key is Singaporean's buying (and working in Singapore - commuting). The 3rd pool of users of the real estate are retirees (Malaysians, Singaporeans and others). I would put vacation homes... as 4th, after all those others.
At the current time many sales seem to be going to investors. Those investors can sell to other investors but that is not a sustainable model for increasing prices. Investors have to sell (or rent) to users of the properties.
The most important strategies for Malaysia to encourage the real estate market in the Iskandar region therefor to me are 1) attracting high paying jobs 2) making it easy to commute and travel between Singapore and JB and 3) making it reasonable for foreigners to invest.
1) is important for high cost housing (which is mainly what this board discusses)
2) is important for both those that want to commute and for say Singaporeans that want to retire to JB (or buy their parents a place in JB) - For some commuting times are important for others they just need it convenient for say weekly trips.
3) both making it reasonable for foreigners to buy real estate (increasing demand) and reasonable for large investments (factories, back office high rises...) that will create high paying jobs. It seems to me a big way to jump start things is to get companies in Singapore to move some back office jobs to JB. This can both decrease the companies cost and provide good paying jobs in JB. It also is a big incentive for those people to live in JB. Many people commute from JB to Singapore but some don't want to do that, if their high paying job can be located in JB that would make more happy to live in JB.
For several of these education for kids would be useful. Would encourage high income workers that want schools for their kids to consider the area. Medical care would be good both for high paying jobs and especially for retirees (and young families).
Several recent posts mention renting to expats (and whether this market is realistic...). I see one big potential market (that is small now): exapts on MM2H visas
http://www.mm2h.gov.my/ This is an attractive visa option that isn't really available in Singapore (unless you are
very wealthy). Right now many MM2H live in KL or Penang but JB is a very attractive option (especially with the proximity to Singapore). It seems to me at this time MM2H expats are not really considering JB. I think there could be a very large increase in this demand over time.