do your research before you go into even think about property develoupment - it can be an absolute minefield. it could even be worth doing some courses on it if very interested. Be aware of tax implications on the income from rent, it could be worth selecting a mortgage which allows you to 'overpay' your monthly mortgages. If you can show all rental proceeds have gone into the mortgage, you won't have tax to pay supposedly.
I'm thinking of investing in somewhere such as bulgaria, and have even been out to explore a little (but it depends on how quickly I can turn around really) But it's something that you have to have the capital in place for (you seem like you might in the future, which is v fortunate!) It requires quite an indepth analysis to decide how risky it is, but the usual euro pros acompany it, as well as its increasing popularity with tourism etc, but then prices arent absolutely stable, so its a risk at anyrate. prices can plummet if the area isnt right, or becomes overdevelouped. Investing here seems much 'safer' and more of a determined and managable investment than abroad.
you also need an idea of what you plan to do with the property(s). and how much time you can devote to it. Are you looking for investments, or revenue? Are you buying cheap, in need of modernization/renovation - what is your budget to buy and renovate (not reccomended without some sort of proffessional guidance), do you plan to buy, renovate then rent, will you convert properties into flats, will you buy renovate and sell straight away?
Will you even take out a mortgage, if so, what is your budget plan for repayment or early repayment? How long a turnover do you want etc..
Don't overlook seemingly minor legal and logistical attributes..