Advice on relocating to Malasiya

You do not say what field you work in, but I am going to assume it is IT software engineering because those are mainly the jobs available in Malaysia.  I am a little concerned that the company is a start-up - because that usually has an impact of their ability to hire foreigners or become a MSC status company.

Accommodation is the largest expediture, so having that paid for is an advantage. However, it is highly unusual to be offered actual accommodation for a family, so I assume it is a monetary allowance (which will be taxable by the way). 

The next largest expenditure is schooling. You can expect to pay from RM1k upwards per month for full day. Cost will depend on type of school and location - which should preferably be close to your workplace and accommodation.

It would be wise to do some due diligence because there are job scams going on here. You naturally do not need to pay any hiring or other fees to an employer or their representatives.

You need to have immigration clearance to even enter Malaysia to work - called a VDR (visa with reference). Apparently the hiring clearance (Stage I approval) and the VDR are taking at least 1 month to complete. Without the Stage I approval from immigration, it may be unwise to resign your current position (in my opinion).

You would pay 28%* tax until you have been in Malaysia working for 182 days (status being tax non-resident), but after that the whole of the tax year (they follow the calendar years) will be retroactively viewed as being tax resident and the stepped system applied. Rates on the first portions of the salary start at 1% and gradually rise. Only the upper portions of annual salary are taxed at high levels (not the whole salary). Divide calculation by 12 to see monthly tax payable. The steps are shown here: http://lampiran1.hasil.gov.my/pdf/pdfam/01_2017_2.pdf

*any amendment to tax rates for 2018 will be announced in the upcoming Budget

Your monthly expenditure for groceries will probably be around RM1k per month. Utilities will be under RM500. Hiring a car will cost around RM1.5k per month. The Indian High Commission website for Malaysia explains how to get your licence attested for use here (important). It is possible to get a one year subscription to internet (TIME is the best provider) but it is necessary to persist in getting this as usually all the companies want to sell 2 year contracts. Basically there is a RM500 fee charged for the one-year contract (usually) but breaking a 2-year contract costs about the same.