Two rented flats each look financially manageable when considered separately. Both plans, however, draw on the same private reserve. A separate view can then conceal the shared bottleneck. This editorial aide organises simultaneous payment burdens; it is neither an investment recommendation nor a forecast on rental, value or yield.
Mark the actually shared source of funds
Map out which income and expenses are assigned to each property and which funds in the background are intended for both. An amount in a private account is not present twice just because you list it in two property overviews as a security.
Finanznavi recommends a structured comparison of income and expenses. [BUDGET] For the question posed here we extend this general method with a shared timeline. The extension is an editorial recommendation, not a regulatory requirement.
Look at concrete periods instead of only annual results
Choose a sequence of months appropriate for your planning and enter the payments actually expected. Distinguish confirmed amounts, plausible estimates and deliberately hypothetical burden scenarios. A positive annual balance alone does not tell you whether all assumed payments are covered on their respective dates.
Then examine a variant in which two adverse events fall in the same period. You are not asserting that they will occur. You are investigating the limit of your financing if both need money at the same time.
Example: Two separate shortfalls share one reserve
In a completely fictional scenario Flat A temporarily needs an additional 3.000 euros, Flat B in the same period needs 4.000 euros. The shared free reserve amounts to 5.000 euros. Each individual shortfall could be covered from it; together, however, they total 7.000 euros of need and therefore 2.000 euros uncovered.
The figures are not market values and not a recommended reserve ratio. The calculation step merely shows the overlap. It would be wrong to deduct the reserve in full in each individual overview and then present both results as secured at the same time.
Do not invent the reaction only when the bottleneck occurs
Discuss identified shortfalls with appropriate financing or tax advice before taking on another commitment. Which expenses can be adjusted, projects postponed or funds actually made available depends on the individual case. Do not assume a sale, new financing or a quick relet as certain simply because the table would otherwise turn negative.
Private expenditures outside the two properties also belong in the common consideration, insofar as the same funds are needed for them. A reserve can only be free to the extent that it is not already allocated to other actual commitments.
In the end you do not receive a guarantee against defaults. But you will know more precisely whether your two individually plausible plans are claiming the same source of funds multiple times. This transparency is the basis for a robust individual review before an additional purchase or a new measure further reduces the shared leeway.