any one deal with 4- plex income property.
can you share some insights on what you need to know as far as cash flow and what to look for .I have a client interested in them

It depends on what your investor is looking for.
Cap Rate or GRM? There is Cash on Cash too but I haven't had many investors use the method.

NOI/Price = Cap Rate
(NOI: Gross Operating Income less all operating expenses). The Cap Rate is: The percentage of sales price available for the loan payment.

Sales Price/Gross Rental Income = GRM
This is a "quick read" for investors when the operating expenses are not known.

Good Luck -

could you give an example say 450k 4-plex
income 30,000 maybe 2000k expenses per month

You are gonna have to provide more info than that for an accurate answer.
Fill in the missing numbers.
Purchase Price $450,000
Cash Invested $????
Depreciation? Is it being depreciated over 3 categories or 4 categories?
GOI: $30000
NOI: $16000
Debt Service ????
Principle Reduction ?????
Tax Bracket ????

The operating expenses on a 4=plex should always be know as the owner should have filed a schedule E on the property. I always request the past 5+ years of schedule E for my clients or if I am the potential buyer. GRM is a bad way to buy properties! I have seen some very bad results from buying investment property using only that value.
Those schedule E's will also give you a good picture as to what maintainence items have been neglected.

The quickest and easiest book on the subject I have seen so far is:

The ABC's of Real Estate Investing, Ken McElroy

Less quick and easy are the following:

Real Estate Finance & Investments, Brueggeman/Fisher
Investment Analysis For Real Estate Decisions, Greer

Both of the above are graduate level text books. Once you have read and understood them, there are darn few questions you will ever get that you won't know the answer to.

I would just go with the McElroy book to start and if you want to take things to a whole different level, think about the other two books. The McElroy book is going to give you a much more practical approach that you will want to fully digest. It's even worth reading more than once to really internalize what he has to say.

Check your state for what the standard is there, but here in California, all the same disclosures, etc. apply to a 4 unit as do to a single. That does not change till you get to more than 4 units.

Good Luck,
R